Sleeping with my father in law (f4m)

 I'm looking for it to be my girl and her boyfriend/ fiancée father. 

I have a plot idea where my characters boyfriend/fiancée has been cheating on her and she finds out. He also plans to screw his dad over big time,  he finds out, breaks in to find evidence to protect himself from his sons plans.

He finds my girl alone & asleep, knowing his son is cheating and has had an obsession with his sons girl and can't control himself . 

She will be fine with everything due to wanting revenge on her ex. There will be sweeter moments and more possessive moments, as i want theme to build a relationship. There should be power play, age gap and size difference. And possibly cnc/somnophilia 

I am happy to discuss and make changes to fit tge plot

It works with my lycan characters well.

I am looking for someone who can write multiple paragraphs and write darker themes. I prefer characters that lean more into 'alternative' appearance