Example: Julian, blonde, in same class, 3rd and 4th grade Sister: Kiera, two years younger, big hello kitty fan Mother: Monica, red hair, glasses. Dad: ??, looks like Ron Swanson.
I just fill in the blanks when I learn them. By the time I'm exchanging phone numbers, I usually have the names down.
Families move and friendships change, so I don't invest a lot of time memorizing details.