Gives nose/forehead kisses
Ezreal gives the nose kisses, Sona gives the forehead kisses.
Ezreal. Sona doesn’t have reason to get jealous - he’s always trotting after her like a loyal puppy.
Picks the other up from the bar when they’re too drunk to drive
Sona would be picking up Ezreal - if he were old enough to drink.
Takes care of on sick days
Sona takes care of Ezreal. She’s got the Aria of Perseverance after all, and more medical experience. But when she’s sick, Ezreal panics and runs around getting every kind of medicine and healing advice from all of the other Supports with heals. ( it gets to the point where most of the Supports with heals are probably going to start considering teaching him minor healing magic. )
Drags the other person out into the water on beach day
Both, equally. They can be cute children sometimes.
Gives unprompted massages
Ezreal - he’s a touchy-feely guy. That, and unlike Sona any pains he’s used to dealing with because of his adventuring behaviors. Sona might not be used to it given her background as a gentle musician, so any back massages or shoulder massages are most likely beloved by her.
Sona drives, Ez gets shotgun - if cars existed on Runeterra, that is.
Brings the other lunch at work
In a modern version of Runeterra, Ezreal would be brought lunch by Sona - that is, if he were old enough to have a regular job instead of his exploring.
Has the better parental relationship
Neither do - Ezreal’s mother died when he was very young, and Sona was an orphan. In a sense, Ezreal might, but he was that typical rebellious child and did fight with his mother a lot despite loving her.
Tries to start role-playing in bed
Ezreal. Though it probably wouldn’t go - hard to sexually roleplay when one of you is mute. ( though he tries. oh does he try. )
Embarrassingly drunk dancer
Ezreal. That is, if he were old enough to drink.
Still cries watching Titanic
Both. They’re emotional messes sometimes.
Firmly believes in couples costumes
Ezreal. Just. Ezreal. He’s that much of a fucking dork.
Breaks the expensive gift rule during Christmas
Both. Ezreal would break his pocket spoiling Sona, and Sona’s got the money to give Ezreal anything he wants due to her musician career.
Makes the other eat breakfast
Sona makes Ezreal breakfast. But some days Ezreal does to repay Sona for caring for him and loving him back.
Ezreal would hyper-remember and Sona would remember as well. Ezreal would hyper-remember because he’d never forget anything concerning Sona - he even remembers every single victory or defeat on the Rift with her as his Support. All the enemy team, his team, their builds, ecetera.
Ezreal, surprisingly. He’d want to have a child with Sona, not only to cement his love for her but also show proof to the world that she is his and his alone.