Love, Incest and Horror(F for M)

[LittleKitten]

He's insane, a psychopath. He murdered his family! They may have beat him and abused him but surely, they didn't deserve to be murdered! At-least he sparred his baby sister. The monster disappears after his crime, vanishing without a trace.
Years pass and his baby sister is now a young woman and he's never forgotten her.

Oh no, he wants her with him and not just in a brotherly sense. On her 18th birthday, he reappears to murder her adoptive family and reclaim her