What I remember of the story is this, and I hope I am not combining several stories into one:
Man comes home early and finds his mother in bed with an old schoolmate that used to bully him. He does not confront them, instead packs his belongings, changes his name and moves to another city.
There he lives above a restaurant, owners become like his new family. A couple of years later his sister finds him and they start a relation. Later his grandfather tries to force them apart.
There is very little sex in the story, more about his journey to find himself.
