The more I let this go the more it comes back stronger in my mind. I would love to a RP with either a brother or brother in law. The husband is deployed or for some reason out of the country and asks his brother or her brother to watch over his wife.
Maybe he moves in with her or vice versa to take care of her more.
Things go from there. The bro/bro in law can be dominant if he wants or if he wants to sway her with romance that works.
Maybe he has always had a thing for her and there is no one else around so this is his time to show it. There can even be forced pregnancy if you want.
This is really an open SL and could be played so many ways. Willing to discuss if interested PM me.
MY On/Offs and RH are listed if you care to read them first.