I've read a lot of these, but this one is sticking in my head and I can't find it anywhere.
It starts with this brother who is talking to his sister and maybe her friend, when his sister leaves. Then his friend makes up an excuse to leave in a hurry. The brother goes behind the neighbors house and looks in the back window to find his sister on her knees, sucking his buddy and maybe some other guys.
He ends up investigating more and finds his mom is also being blackmailed.
It's multi-chapter and has a one or two word title, if I remember correctly.
