Given that Norma's brother did not deny the accusations but said "it wasn't like that", you almost have to wonder if whatever happened between the siblings was consensual or if one or both was/were harmed by one of the parents. Rewatching it, it seemed as if the brother wanted to say something else about Norma but held back.

Also for someone who is supposed to be a geeky weird nerd, Norman certainly has the young ladies showing interest in him. lol

"When the snows fall and the white winds blow, the lone wolf dies but the pack survives."
Winter is Coming

Now this is the Law of the Jungle—as old and as true as the sky; And the wolf that shall keep it may prosper, but the wolf that shall break it must die.
As the creeper that girdles the tree-trunk, the Law runneth forward and back; For the strength of the Pack is the Wolf, and the strength of the Wolf is the Pack.