Ed is systematically abused by both Sarah and her mother, which probably doesn't get better when you consider how... Special he is at times. His dad evidently isn't very much present anymore, coming home and crashing in front of the TV each evening. When Ed is grounded, they also dismantle the staircase to his basement room and fit the door with a heavy duty bolt. Their marriage is going down the plug, their son is mentally challenged and their daughter is a little tyrant. How long will the facade of wholesome suburban life last?
Edd is unseen and unheard by his parents, who only acts in his life through left post-it notes, detailing his daily chores and tasks. He is also pushed pretty hard through school, no doubt "destined" for greater education, wether he like it or not.
Another theory exist on the matter, as well...
http://i0.kym-cdn.com/photos/images/original/000/298/976/a59.jpg
Eddy, in turn, long lived in fear and pain beneath his older brother's thumb and uncaring parents. Eddy could never truly get past what his brother did to him, almost having a stroke of Stockholm Syndrome to how he remade the memory of his tyrant brother into a kind, cool guy who looked out for and respected his little bro. There is much boiling and churning beneath that suave, scheeming facade he has erected for himself, which he can't yet find the courage to challenge.
Rolf and his family fled from the bloody civil wars of the Balkans, being granted asylum and citizenship in the United States, eventually settling in Peach Creek. Unable to cope with their flight, Rolf still to this day attempts to live the life that his ancestors had done before him, before his land and heritage were cruelly snatched away, growing crops and raising cattle on the small, suburban back yard. He is a son of a shepheard with no herd to lead.
His often mentioned nanna, supposed to be living in the Rolf household but never seen, didn't set foot outside their homeland, killed in the civil war.
...This is rather fun in some horrible, horrible way. Forgive me, Edboys...