Okay, main character could have a shy neighbour girl who might have a crush on him - she's 17-18yo, in high school, wants to become a scientist... (not athletic, so self-conscious)
She might have an annoying brother (or sister) or other relatives (eg cousin/s etc?)
Her sister wants to become Britney Spears and win American Idol
He could also have 2 younger sisters, OR brothers (or one of each) still in primary school - maybe annoying/endearing (?) Either small one/s or pre-teens/teens (you mentioned Cosby show/Full House, they had a mix of kids and teens there)
One of them HATES sports (?)
Or, if he's an only child, he could be 'spoilt' by parents, and his coz who's more 'tough' (& uncle/dad/mum...?) keep/s throwing it back at him?
Mum is a reserach scientist (or celebrity chef?) and wants him to 'focus'? hm?
If he left college his parent/s could keep telling him he's a bad example for the others?
(Oops, did he leave college? hehe, or is/was it just my interpretation?)
Just some thoughts... Keep or leave as you wish...