Yaoi

So, there was this story, seme was straight and had a girlfriend. The girlfriend wanted threesome and discussed with his boyfriend. Ml didn’t want to but since his girlfriend wanted it, he relented. So the girlfriend asked her male friend(who probably was her ex too, can’t remember clearly), for threesome. the male friend agreed.

Then, they had threesome. They have it once, leading to more times and, sparks start to fly between the girl’s boyfriend and her (ex) male friend.
It’s from the gay novel: Straight guy series Book 2. I read it years ago. https://www.goodreads.com/book/show/55218452-just-a-bit-obsessed
So if you know something of similar kind, pls recommend(only gay/bl/yaoi with older seme).