mado/albedo (broship of course)
Send me a ship and I’ll tell you:
who holds the umbrella when it rains: Albedo though it's Mado's umbrella and him having to crouch down to fit under it because she's short is uncalled for. If only he could get to his Galvan form then she could hold the umbrella for them instead.
who is the grumpiest in the morning: Albedo because angry science frog, grumpy for like 23/6 at the least
who worries more when the other is sick/hurt: Mado. Albedo does worry for her health since he's aware that human children are delicate and stuff but for him it's not always very obvious when she's not well, specially if it's psychological and not physical.
who plays pranks on the other: Neither, Albedo finds this human activity dumb and pointless, Mado simply isn't really much of a pranker.
who is always the first to suggest cuddling on the sofa: Mado, because she doesn't want to invaded Albedo's personal space nor make him uncomfortable, as she knows he's not one for physical contact much. If he denies, she backs away.
who insists on creating nicknames for the other: Neither. Again, Albedo thinks this habit is useless and his nicknames towards others are usually ones that insult their intelligence or their species, so he keeps those away from Mado. And apparently Mado's one's of the few who firmly calls him by his name instead of filling him with puns such as "Alfredo".
who drools on the other when they’re asleep: ... surprisingly, Albedo does. Mado is not amused and shrugs it off. If he were to be faced about it, he'd mostly likely blame this unsanitary and undisciplined habit on Ben's DNA.
who says ‘I love you’ first: Mado because Albedo's kinda unfamiliar with displays of affection, be them platonic, familiar or romantic or whatever, though he appreciates Mado's nurturing nature towards him regardless.