Is a serious relationship possible

2 months ago I got in contact with this guy I had a"thing"with over 15 yrs ago, we lost contact till now. He told me how he's told people about things that happened between us back then..in the bedroom.2 weeks ago I was forced to move out of my home due to my daughter's violence.my friend told me to move there his for is always open for me.We've been catching up..He is dying his ex of 3 yrs..it seems to be only cuz she helps him with car etc., he is also in live with this other woman he had known since school but she got want him now.I really like this guy, I always have. We do have sex, we share a bedroom although he is gone a lot...He works 7 days a week and when this ex really insist and he feels obligated he will stay the night there. I've been happy single for many months now,I haven't been looking for relationship. But like I said I have feelings for him. He had 3 kids that live with us also. 11,14,17. The daughter is 11, she is really connecting with me. I've been doing what I'm use to doing...cooking for the everyone, cleaning, doing mine and his laundry, grocery shopping.I can tell the kids really like having me there, they have gotten use to fending for themselves basically.I noticed the surprise on his face when he comes home and I'm cooking or bonding with his daughter.I know right now he's not ready for anything more, there are other woman he had sex with, we may end up having a threesome with them...I'm bisexual and we r both very sexual people but I'm happy Wyeth it only being with him (male wise st least). We talk about how he feels, what he's going through emotionally with these women, he asks my advice, I've seen him cry. I'm happy being good friends with benefits with himif I am unable to get more from him.Is it possible? What should I do? I've thought about cutting the sex off, but we really can't resist each other in that way! How can I help him get over that woman and make him realize he don't need that ex to friend on.He's insecure and im pretty sure scared of being alone.The other thing is these 2 woman don't know the"real"him..He hides significant things he does or feels from them but he tells me everything.