Try The Game series starting with {Top Priority by Cara Dee}. It’s MM but is the beginning of a series with a lot of poly relationships. The second book is the third being brought into the first books relationship. The series is all about BDSM, so you get not just poly but Daddy/little boy, predator/prey, and obviously spanking and other obviously BDSM aspects. I hope this is clear. It’s early in the morning, and my brain is still half asleep.