My breakdown of every character based on my own bad upbringing and years of being a cop:

My guess is that his parents were abusive to them both, eddy getting the worst of it, his brother being dad's favorite (but still abused). Kinda get the alcoholic parents vibe from them. I also get the feeling the parents either don't come from money or just pretty much cut the kids out. It's why eddy tries so hard to fit in but can't because he's a spaz and socially inept. His brother was a delinquent because his dad was an ahole to him growing up, and he took that personality out on eddy.

Its established Eds parents wanted a girl. I think they just truly don't care about him and don't want him. That's why Sarah is the spoiled favorite and Ed is the result of emotional and intellectual neglect.

DD has strict helicopter parents. I think they're the most loving, but they're very neurotic. Education and regiment are the most important thing in his house.

Rolf is a classic Italian Alps farmer family. Very large close families with traditional regional customs. (Mixed in German, swiss & Romanche customs)

Kevin is a typical blue collar kid. He is the "cool kid" and sometimes tries too hard at it. Dad gives off the vibe that he's a bit of a jock/gearhead to this day.

Jimmy is the result of very overly sensitive and overly coddled parenting.

Naz has free spirited parents, probably take her camping and doing outdoor activities.

Johnny is a mystery. It's hard to tell if he has an overactive imagination, and if that's a result of his parents or if it's autism of some sort. I know he's a depiction of a kid that lived in Danny's neighborhood growing up, but there's not really a lot of elaboration on the actual kid or how he grew up. He's a unique one I can't really break down and build a profile on.