I'm looking for stories where Sam and Dean have sex because of the Mark of Cain. In particular I'm looking for stories where Sam is doing it to keep Dean close, away from Crowley and/or helping Dean control the impulses of the mark. But any stories that fit this criteria are fine, i.e. if Dean does it as a form of punishment or revenge against Sam, etc.

I also wonder if there are any stories out there where Amara offers Sam to Dean if Dean will stop trying to stop her.

Thanks.