Gives nose/forehead kisses
Sebastian will because those are the only places he can really kiss.
Why do I imagine Aoi will get jealous more often? The Prince is often surrounded by the fairest of maidens, after all.
Picks the other up from the bar when they’re too drunk to drive
Aoi better learn to drive a carriage because Sebastian's a lightweight.
Takes care of on sick days
They both would because they're sweethearts.
Drags the other person out into the water on beach day
Aoi would have to do that. Sebastian's never seen the ocean and would be afraid of waves.
Gives unprompted massages
Sebastian would because he loves unannounced affectionate gestures like that and loves using his hands in a nice, safe way.
Aoi rides shotgun because Sebastian takes the reigns.
Brings the other lunch at work
Aoi would bring delicious lunches because if he doesn't, Sebastian might forget to eat.
Has the better parental relationship
Parental relationship? As in with their own parents, because... their parents are all dead.
Tries to start role-playing in bed
Sebastian would because he's imaginative and he has no choice but to be creative.
Embarrassingly drunk dancer
I promise you, it's Sebastian.
Still cries watching Titanic
Sebastian cries watching clouds, bruh. He's a very sappy guy.
Firmly believes in couples costumes
SEBASTIAN WANTS COUPLES EVERYTHING.
Breaks the expensive gift rule during Christmas
Every gift Sebastian gives is expensive. Houses, horses, carriages, sculptures, nothing would be too good for Aoi.
Makes the other eat breakfast
Aoi would make Sebastian eat breakfast because it's the most important meal of the day and Sebastian always skips it.
Aoi would. Sebastian would try, but he tends to have a bit too much on his mind.
Sebastian would bring it up in little "what-if" scenarios.