Other ideas/relationships that could be fun!

i have ideas that involves little kids: Can we have a school pack based on children? | EA Forums - 11172051 and for toddlers too: Can we have a toddler based pack? | EA Forums - 12111749 

as for the home schooling idea i have this one in mind: Home Schooling game pack idea | EA Forums - 12109479 

as for the sibling rivalry i'm thinking about adding this as a basegame update with the neighbourhood stories, we kind of already have the rivalry that comes with "Growing Together" but they should implement it better in my opinion, i feel like they get along yet don't get along at the same time, if you hate someone so much you can't pretend like you like them, someone made a post about it in which i made a comment they should add rivalry/enemies in the neighbourhood stories: Updated Neighborhood Stories 

i never check the family tree but if not mistaken if you have the neighbourhood stories turned on and you turn adoption option on it's possible to add adopted kids to your household

as for having crushes on someone i agree everybody likes fall in love with each other, it's not realistic, people in real life have crushes but that person might not feel the same way about you, we do have preferences if you have "Lovestruck" pack installed but i do still feel like anyone can have a crush with like everybody and they like feel the same way, it shouldn't be like that others feel the same way about you, they can improve Lovestruck for that part

i heard nanny's are useless so i'd love to hear your ideas they should do more than watching the babies, infants and toddlers, instead they should really take care of them, if not mistaken if you have "Growing Together" pack installed you can let them have a sleepover for a few days, i didn't tried much of it though but if not mistaken they can take care of your houses for sure, they're non-playable character so it's a win-win you won't have to control them

i hope that answers your guestion?