should I stay or should I go

I started seeing this guy I really like him we are practically perfect together! We have been doing the horizontal dance for some time now and it’s starting to get more serious. Which normally would be great the only thing is he has a daughter. It’s weird to start a relationship knowing that he has always and will always love someone else more then me. I know that he should love his kid more it’s just weird to think about. Also I know I want kids of my own some day and if it’s with him idk if he would love them the same way he loves her maybe I’m crazy. Do you think I should stay with him?