Preface

One Piece Older Sibling Headcanons
Posted originally on the fanfiction.lol at https://fanfiction.lol/works/1080.

Rating:
General Audiences
Archive Warning:
Creator Chose Not To Use Archive Warnings
Categories:
General (non relationship-focused), Y/N (reader insert)
Fandom:
One Piece (Manga)
Relationships:
Whitebeard Pirates (One Piece) & Reader, Mugiwara Kaizoku | Strawhat Pirates & Reader, Akagami Kaizoku | Red-Hair PIrates & Reader, Heart Pirates (One Piece) & Reader, Kiddo Kaizokudan | Kidd Pirates & Reader
Characters:
Whitebeard Pirates, Mugiwara Kaizoku | Straw Hat Pirates, Kiddo Kaizokudan | Kidd Pirates, Heart Pirates, Gender Neutral Reader
Additional Tags:
Fuff and Angst, Found Family, Headcanon, short & sweet
Language:
English
Series:
Part 10 of One Piece x Reader
Stats:
Published: 2026-11-02 Words: 4,556 Chapters: 10/?

One Piece Older Sibling Headcanons

Summary

a collection of headcanons about how one piece characters would act as older siblings

Chapter 1: Marco

Older brother Marco who is protective of you but not in an overbearing way


Older brother Marco who makes you have bi-weekly check ups just to make sure you're ok though he does that with most of your other siblings as well.


Older brother Marco who If you have a bird devil fruit, will be very happy to help teach you how to fly. He would love to just go on flys with you to get away from the chaos of the ship or to enjoy the views of the ocean or island you're docked at.


If you ever have trouble sleeping or have any type of nightmare that stops you from falling back to sleep, older brother Marco is almost always up and in his office in the med bay if you just need to be near someone for a bit.


Older brother Marco who if you want and ask enough times will lay down with you to try and help you sleep and eventually you both end up falling asleep together. Haruta and thatch may or may not have taken pictures of the two of you for Pops.


Older brother Marco who will subtly push you to talk to people your age whenever the crew stops at an island.


Older brother Marco who worries about you not having any friends your age to talk with.


Older brother Marco who will feel so much relief if he sees you having fun with people your age.


Older brother Marco who doesn’t react if you snap or yell at him for no reason because he knows you don’t mean any of it.


Older brother Marco who will sit with you in silence for however long it takes for you to calm down so you can talk everything out and figure out what upset you.


Older brother Marco who no matter what will always be there for you even if you try to push him away he will be patient and wait for you to be ready for his help

Chapter 2: Thatch

Older brother Thatch who will learn to cook anything you want because he'll do anything for his favorite little sibling.

 

Older brother Thatch who will do anything in his power to make you happy if you're in a bad mood.

 

Older brother Thatch who teaches you how to cook your favorite foods so you won't have to rely on anyone for it.

 

Older brother Thatch who helps you with anything you ask even if he has no clue how to help because he is weak for his adorable little sibling.

 

Older brother Thatch who sneaks you desserts even if Marco said you shouldn't be allowed any.

 

Older brother Thatch who is your number one ride or die whether you like it or not.

 

Older brother Thatch who will die of happiness if you say he's your favorite brother. He will also proceed to gloat about it for the rest of time much to everyone else's dismay.

 

Older brother Thatch who will stay up all night and bake with you if you have a nightmare and don't think you can go back to sleep.

 

Older brother Thatch who will hold you all night long if that's what you need.

 

Older brother Thatch who does his best to try and figure out what's bothering you if you refuse to tell him because there's no way he's gonna let you fester in all your negative emotions alone.

 

Older brother Thatch who tells you jokes that he thinks will make you laugh or at least smile when you're upset.

 

Older brother Thatch who will tell you any and every story that comes to his mind if you ask.

 

Older brother Thatch who may over exaggerate the craziness of the stories to make you smile.

 

Older brother Thatch who will bring you a bunch of different snacks when you are upset because what's a better way to make yourself feel better than a few sweet treats?

 

Older brother Thatch who will deny having a massive soft spot for you even though everyone knows it's true.

Chapter 3: Haruta

Older brother Haruta who will drag you into his pranks if he sees that you're feeling down.

 

Older brother Haruta who will not hesitate to prank you just as much as everyone else.

 

Older brother Haruta who will be over the moon if you manage to successfully prank him back.

 

Older brother Haruta who will use any of the connections he's gotten over the years to help get you whatever you want.

 

Older brother Haruta who panics so badly if one of his pranks go too far and actually upsets you.

 

Older brother Haruta who will do anything to make it up to you. Be it buying you something you want or doing anything you ask him to.

 

Older brother Haruta who will push through the teasing that everyone else is sending his way as long as he can get into his favorite little siblings good graces again.

 

Older brother Haruta who will be so relieved when you finally forgive him that he can't resist the urge to give you the tightest hug he can.

 

Older brother Haruta who will get you to help him prank everyone who dared tease him earlier.

 

Older brother Haruta who will throw away all of the jokes if you need him to be there for you when you're upset.

 

Older brother Haruta who will drop everything if he hears you got hurt even if it was just something minor.

 

Older brother Haruta who will "jokingly" ask if you want him to train you with a sword but in reality he's worried about you and wants to make sure you can protect yourself if you ever get separated from the crew.

 

Older brother Haruta who gets giddy when you actually agree.

 

Older brother Haruta who almost bites Vistas head off when he tries to get in on your training because you agreed to get trained by him! Not Vista!

 

Older brother Haruta who will not hesitate to knock you on your ass while training.

 

Older brother Haruta who is so insanely proud of you for all the progress you’ve made and will make sure you know it.

 

Chapter 4: Nami

Older sister Nami who lost her shit at you when she realized you somehow followed her when she left Cocoyasi village to join the strawhats. Luffy confesses to hiding you on the ship and he gets sent flying.

 

Older sister Nami who forces you to help her scam as many people as you can as a punishment.

 

Older sister Nami who will give you a bigger allowance than anyone else. Don’t tell anyone though she doesn’t need to hear Luffy's whining.

 

Older sister Nami who won't fall for your begging no matter how much you do it. Sorry she's 100% immune.

 

Older sister Nami who will jump to your side to protect you no matter how scared she is if there is any danger.

 

Older sister Nami who forces Sanji to carry all your bags as the two of you go on a shopping spree together.

 

Older sister Nami who demands that either Zoro or Sanji(or both) train you so you can protect yourself against anything that might try to hurt you.

 

Older sister Nami who will sit and talk to you about home whenever either of you are feeling homesick.

 

Older sister Nami who trades stories with you about Bell-mère as a way to honor her memory.

 

Older sister Nami who will be annoyed at you for waking her up in the middle of the night until she realizes that it was because you had a nightmare and she enters full on overprotective sister mode.

 

Older sister Nami who will cradle you in her arms and ask you about your nightmare. If you don’t wanna talk about it then she’ll just hold you till you both fall asleep.

 

Older sister Nami who will whack you on the head if you ever try and say you are too old to cuddle with her. You’ll never be too old to receive your big sister's love!

Chapter 5: Zoro

Older brother Zoro who makes sure that you know how to wield a sword.

 

Older brother Zoro who gets so pissed when you team up with Sanji to make fun of him.

 

Older brother Zoro who blames you for always getting him lost.

 

Older brother Zoro who makes you sit on his back as he does push ups.

 

Older brother Zoro who gets annoyed at you for just breathing too loudly next to him.

 

Older brother Zoro who will physically fight you if you provoke him enough.

 

Older brother Zoro who loves to spar with you but will never admit it.

 

Older brother Zoro who will throw you over his shoulder and run away with you if he thinks you’re spending too much time with Sanji.

 

Older brother Zoro who will call you stupid for doing something and then turn around and do the same thing.

 

Older brother Zoro who will get all embarrassed if you correct him on something he says or does and he will claim he already knew that and he was just “testing you”

 

Older brother Zoro who is glad you agree with him that if you’re going to die in wax you should at least do a cool pose.

 

Older brother Zoro who calls you pose lame.

 

Older brother Zoro who gets smacked by you as soon as the two of you are out.

 

Older brother Zoro who blames you when the both of you get in shit with Nami.

 

Older brother Zoro who isn’t the best with emotions so he really isn’t sure how to help you when you're upset.

 

Older brother Zoro who gets some unsolicited advice from Robin about how to comfort you better.

 

Older brother Zoro who fails so hard that it actually ends up working and making you laugh.

 

Older brother Zoro who's more than a little confused but you’re not sad anymore so that's a win in his book.

Chapter 6: Buggy

Rodger pirate era

 

Older brother Buggy who is so flippant with how he treats you that it makes you dizzy.

 

Older brother Buggy who will be all up in your business trying to spend time with you but as soon as anyone (especially Shanks) comments on it he's already on the other side of the ship grumbling under his breath about how stupid everyone is.

 

Older brother Buggy who feels bad if he actually upsets you by running off like that so as soon as no one is paying attention he'll go apologize (in his own Buggy way there's no way hes actually saying sorry) and go back to hanging out with you if that's what you want.

 

Older brother Buggy who gets jealous if you spend too much time with Shanks.

 

Older brother Buggy who will run over and snatch you up right under Shanks' nose if it goes on for long enough.

 

Older brother Buggy who will say he doesn't care about you while he holds you like you're going to disappear.

 

Older brother Buggy who acts annoyed if you follow him around but on the inside his heart is doing flips.

 

Older brother Buggy who rubs it in Shanks’ face whenever you choose to leave him for Buggy.

 

Older brother Buggy who gets you to help him with making fun of Shanks.

 

Older brother Buggy who holds himself back from yelling at you if you ever mention his nose. Roger pointed that out once and Buggy's face went so red that his nose blended right in.

 

Older brother Buggy who if you have longer hair will learn how to style it any way you want as long as you don’t tell anyone.

 

Older brother Buggy who will does his best to keep you (and himself) as far away from any battle the crew has as possible.

 

Older brother Buggy who gets so caught off guard if you go to him for comfort after you had a nightmare.

 

Older brother Buggy who tells you to go to Roger or Rayleigh instead but not because he doesn’t want to help you but because he doesn’t trust himself to comfort you proporly.

Older brother Buggy who will automatically give into you if you even get slightly close to crying.

 

Older brother Buggy who will reluctantly let you climb into his bed and cudle up with him.

 

Older brother Buggy who says you have to leave as soon as you feel better but when he looks down at you you’re already passed out against his side.

 

Older brother Buggy who debates picking you up and carrying you back to your bed but as soon as you grip onto his shirt in your sleep he throws that idea out the window.

 

Older brother Buggy who wakes up to Roger taking pictures of the two of you sleeping and end up yelling at him making you wake up.

Current day

 

Older brother Buggy who truly hasn't changed much since you were kids.

 

Older brother Buggy who still has a massive soft spot for you and will continue to deny it till the day he dies.

 

Older brother Buggy who may be weaker then you now but he will still act like your some small defenseless kid.

 

Older brother Buggy who demands you call him at least once a week and if you don’t he will find a way to show up and yell at you even if you're on the other side of the world.

 

Older brother Buggy who makes sure you know he doesn’t care about you or Shanks even though you know he keeps a picture of you three next to his bed.

 

Older brother Buggy who will try to murder you if you tell his crew stories of when you two were kids.

 

Older brother Buggy who runs his mouth about how he never wants to see Shanks again and how he hates him and blah blah but will automatically give in if you ask him to come visit Shanks with you.

 

Older brother Buggy who is still gets jealous if you spend to much time with Shanks and not him

Chapter 7: Koby

Older brother Koby who did his best to protect you while you were both on Alvida's ship despite how scared he was.

 

Older brother Koby who makes sure you stick near him no matter where you are so he can make sure you're safe and ok.

 

Older brother Koby who will do all your chores for you if you aren't feeling good.

 

Older brother Koby who will give you his portion of food if your still hungry after meals. Doesn't matter how much you refuse it he will keep refusing your refusal until you take it.

 

Older brother Koby who does his best to be a good example for you despite the situation you're in.

 

Older brother Koby who will have a heart attack if you stand up to any of the pirates because they're being rude to him or you.

 

Older brother Koby who will patch you up of you end up getting hurt by them.

 

Older brother Koby who feels like a bad brother for not being able to protect you.

 

IF YOU BECOME A MARINE

 

Older brother Koby who's relieved that you became a marine with him. Mainly because he can keep a better eye on you this way.

 

Older brother Koby who trains even harder then he does normally because he has you and he needs to be able to protect you from everything.

 

Older brother Koby who worries about you if you start to train as hard as him.

 

Older brother Koby who gets a little huffy if you call him a hypocrite for being fine with pushing himself that much but not being ok with you doing it.

 

Older brother Koby who may get told off by Garp for hindering your training. He may be worried and scared that you're going to hurt yourself but that doesn't mean he should stop you. He can't expect you to rely on him forever.

 

Older brother Koby who finally let's it up but don't expect him to stop being a massive worry wort over you!

 

Older brother Koby who will patch you up himself if you don’t want to go to the med bay.

 

Older brother Koby who stays awake with you talking to you in the barracks whispering so you don't wake anyone else up like when you were on Alvidas ship.

 

Older brother Koby who does his best to not let you and Helmepo be alone together because the last time that happened it ended with him getting teased by you two about things he did as a kid. He of course tried doing the same to you but Helmepo only cared about Koby’s embarrassing stories, not yours.

IF YOU BECOME A PIRATE

 

Older brother Koby who isn't mad that you joined Luffy but that doesn’t make him any less worried.

 

Older brother Koby who almost joins Luffy's crew with you because he is that hesitant to leave you.

 

Older brother Koby who finally gives in and lets you join Luffy's crew while he joins the marines after you quite literally kick him in the ass.

 

Older brother Koby who is so distracted worrying about you that he ends up getting in trouble for slacking.

 

Older brother Koby who watches the newspaper like a hawk waiting to see your face on a bounty poster because he knows it's only a matter of time.

 

Older brother Koby who will still almost die from worry when you do finally get a bounty poster.

 

Older brother Koby who wants to be proud of you but he's too busy worrying to do that.

 

Older brother Koby who needs Helmepo of all people to finally smack some sense into him and get him to realize he can’t spend all day worrying about you.

 

Older brother Koby who then talks about you to Helmepo so much he rivals Ace talking about Luffy. Helmepo regrets snapping him out of his constant worrying now.

 

Older brother Koby who keeps your poster on him at all times so if he's ever missing you or letting his worry get to him he can look at it and remind himself you're following your dream.

 

Older brother Koby who will hug you so tightly when you finally see each other again that it feels like he's crushing you.

 

Older brother Koby who will fret over you like a mother hen looking for any type of injuries.

 

Older brother Koby who will disregard any of your complaints of being fine until he is one hundred percent sure you are.

 

Older brother Koby who will thank Luffy and the rest of the crew for looking out for you and taking care of you.

 

Older brother Koby who gets an ego boost if you comment on how strong he is now.

 

Older brother Koby who will not hesitate to tell embarrassing childhood stories if asked by Luffy or someone else.

 

Older brother Koby who is so proud of you that it brings him to tears.

Chapter 8: Sanji

Older brother Sanji who gets you to taste test all the new food he makes before anyone else.

 

Older brother Sanji who makes sure there are always some of your favorite snakes around.

 

Older brother Sanji who gets so over dramatic if you don't like something he made. He will be on the ground and acting like you shot him till you just walk away.

 

Older brother Sanji who always keeps an eye on you. He knows you can handle yourself in most situations but he can help but feel a bit overprotective of you.

 

Older brother Sanji who gets you to help him with cooking or baking when you’re upset or in a bad mood.

 

Older brother Sanji who will get mad at you if he ever catches you smoking because he doesn’t need you destroying your lunges, call him a hypocrite all you like he doesn’t care.

 

Older brother Sanji who gets mad at Luffy, Usopp, and Zoro quite often for being a bad example to you.

 

Older brother Sanji who feels betrayed when you team up with Zoro to tease him.

 

Older brother Sanji who will always prioritize you over everyone else no matter who they are.

 

Older brother Sanji who trains with you all the time so he can make sure you can defend yourself if you get split up from the crew.

 

Older brother Sanji who feels like he’s failing you if/when he loses a fight.

 

Older brother Sanji who gets so worried that he would do something wrong or that he won't be strong enough to protect you and you will start to hate him that he sometimes pushes you away and causes you to become upset and sad.

 

Older brother Sanji who used to get yelled at by Zeff for it and now is getting yelled at by Nami.

 

Older brother Sanji who feels like shit for letting his worries get the best of him and do the exact thing he was trying to prevent.

 

Older brother Sanji who apologizes with both words and your favorite food.

 

Older brother Sanji who has a weird sixth sense for when you are having a nightmare and wakes up and goes to you before you even wake up from it.

 

Older brother Sanji who will carefully wake you up and is not surprised when the first thing you do is hug him and bury your face in his chest.

 

Older brother Sanji who understands all too well what your nightmares are about.

 

Older brother Sanji who is willing to listen to you talk about it if you'd like. If you don't then he will find a way to distract you from it. Be it by playing some type of game or making food.

 

Older brother Sanji who will tell you how proud Sora would be if she saw you today if you ever start to doubt yourself or if you start to think that you're gonna turn out just like Judge.

 

Older brother Sanji who will probably start to cry if you say the same back to him.

 

Older brother Sanji who no matter what is proud of you for turning out the way you did and not becoming like the rest of your family.

Chapter 9: Kidd

Older brother Kidd who scruffs you like a cat and dangles you off the side of the ship threatening to drop you in the water if you annoy him too much.

 

Older brother Kidd who makes you little trinkets but will get annoyed if you tell anyone about it.

 

Older brother Kidd who will carry you on his shoulders if you ask him to but will grumble about it the entire time.

 

Older brother Kidd who will beat the shit out of anyone who he thinks is looking at you weird even if it was a small little glance.

 

Older brother Kidd who will get you anything you want if you give him puppy dog eyes.

 

Older brother Kidd who denies it adamantly when anyone including you point it out.

 

Older brother Kidd who understands what your feeling better then anyone else but still struggles with comforting you when your upset.

 

Older brother Kidd who will just ask you straight up what you want him to do to help because that's better then just sitting there doing nothing.

 

Older brother Kidd who will do his best to do what you ask but there is a limit to it. He will not do anything he deems embarrassing in front of the crew unless there is truly nothing else that will make you feel better.

 

Older brother Kidd who doesn't worry about you to much during battles. He knows for a fact you can handle yourself just fine without his or anyone else's help you are his sibling after all.

 

Older brother Kidd who argues with you all the time over the dumbest shit ever.

 

Older brother Kidd who paints your nails for you so you match with the rest of the crew. If you tell him you can do it yourself he'll just brush you off and tell you he can do it better. When he lost his arm though you started doing it for him instead since its a little hard to do it with a metal arm.

 

Older brother Kidd who yells at Luffy for "stealing you" even though you were the one who went up to him.

 

Older brother Kidd who tells you to stay away from both Luffy and Law, you don't of course why would you listen to his lame ass?

Chapter 10: Luffy

Older brother Luffy who dragged you along with him when he left dawn.

 

Older brother Luffy who will only sleep if he has you wrapped in his arms and legs.

 

Older brother Luffy who has flung you around so much growing up that you’re not even phased by it anymore.

 

Older brother Luffy who has eating contests with you all the time much to everyone else dismay.

 

Older brother Luffy who ropes you into all his crazy shit even if you don't want to go with him. It's fine, this is going to be fun!

 

Older brother Luffy who will jump at the opportunity to play any type of game with you.

 

Older brother Luffy who will happily yap about Ace with you so much that it starts to dive the others crazy.

 

Older brother Luffy who can tell when you’re upset before you even say anything to him.

 

Older brother Luffy who asks you what's wrong in the most straightforward way because he wants to find out what it is as quick as possible so he can punch it.

 

Older brother Luffy who will wrap you in such a tight hug that you can barely breath if you start crying.

 

Older brother Luffy who will be ready to beat the shit out of someone if he finds out anyone hurt your feelings to the point you are crying or on the brink of tears.

 

Older brother Luffy who will absolutely lose his shit if you get badly injured in a fight.

 

Older brother Luffy who will refuse to leave you side until you are fully healed.

 

Older brother Luffy who gets yelled at by Nami and Chopper for laying on top of you while you’re healing.

 

Older brother Luffy who feels like it's his fault you got so hurt even though it most definitely isn't.

 

Older brother Luffy who will need you to smack some scene into his head to make him realize it really isn't his fault and that things like this are going to happen with you both being pirates.

 

Older brother Luffy who realizes you’re right and loosens his hold on you.

 

Older brother Luffy who fails to save you on Sabaody.

 

Older brother Luffy who learns about Ace’s execution.

 

Older brother Luffy who needs to save Ace.

 

Older brother Luffy who breaks into impel down.

 

Older brother Luffy who arrives at Marine Ford.

 

Older brother Luffy who got Ace out of his chains.

 

Older brother Luffy who watches as Akainu punches a hole through Ace’s chest.

 

Luffy who is running him.

 

Luffy who failed.

 

Luffy who lost another big brother.

 

Luffy who doesn’t know how he's ever going to face you after letting him die.

Afterword

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