What is BM in this context? Being rude to them? Dark Magic?
Rogue-like has pretty active threesomes and an addiction-based control aspect, no incest though.
Lilith's Throne is text-based but has incest. Not sure you can have someone else join your aunt&you, but you can always grab 2 of your own daughters. Very customisable, options for slavery too, and you can have at least 5-person orgies with imp gangs (never seen any spawn as relatives). Furry sex is technically avoidable as long as you don't count the aforementioned demons.
I think the old Slave Maker 3 game had threesome actions, the game wouldn't recognise custom characters as being related though (it came with several from Ranma and Ah My Goddess! which might have special incest scenes).
Four Elements Trainer has M/F incest in Book 2 and might include a threesome scene somewhere, I don't think there's anything between blood-related women though (maybe an Azula/Ursa easter egg or something).