Okay so as a sister who has a younger sister with a big age gap I feel qualified to put some tiny headcanons on Marco and Mariposa
Marco tends to spoil Mariposa when he goes out grocery shopping/snack shopping with snacks much to his parents chargin
Because he’s usually watching Mariposa when his parents are busy he ends up watching the shows/movies she likes and gets emotionally invested (A few examples are Sofia the First, The Lion Guard, Elena of Avalon, and Bluey)
Yes he will sing alongside her with the songs
He is never going to out loud admit that he cried during True Colors but Janna knows and blackmails him. Tom makes fun of him at first, then he watches it and is full on sobbing as well.
Mariposa sneaks to use his phone but instead of using it to play games she uses it to take silly photos of herself and others (Karma will strike because he keeps most of them)
She ends up picking up a few of his mannerisms and habits. Like poor conversation skills. (He kinda feels bad about that one)
Their parents definitely track her progress via Marco’s own past and they wouldn’t have minded if he graduated early if this didn’t end up messing up their mile stone map.
All that said Marco does his best to teach her from his own mistakes. Yes she thinks he’s dumb for doing some of that stuff but if talking about it keeps her from doing it he’ll live with it.
Okay, so when she’s still young he knows it’s important for her to learn and to practice walking but she’s just so cute and Coe on who wouldn’t want to hold her?
More than once Angie has had to pry Mariposa off of him.
Raphael doesn’t care. It’s cute AF.
Since Marco’s parents were absent a lot when he was younger (canon based on comics) they’re a lot more attentive with Mariposa and as much as Marco’s happy for his little sister there’s a small drop of bitterness in his stomach knowing he didn’t get that.
As with any good older sibling, the best way to overcome jealousy of the attention is to also give the new sibling lots of attention.
Despite being so young after high school and entering college he makes sure they have time to talk.
She talks to him about her day, what she and her friends did, what he and his friends did, and complaining about school.
Sometimes this is at dinner, sometimes it’s right before bed, sometimes it’s on their devices but they always have a chat.
Despite also being pretty smart, Mariposa tends to struggle getting started on school work and Marco having gone through this is always offering advice and tips.
Mariposa loves riding Nachos and Marco’s ‘safe kid’ reputation comes into play as he convinces their parents that if she’s responsible Nachos is sweet just like any other pet. (And incase of emergencies Mariposa is well equipped to drive her)
