Do he still got feeling for his ex wife

My boyfriend has been really consistent on us start our own family but he has a ex wife and two kids. He called  his ex wife  to see when he can see his kids. But instead they started arguing then she changed the subject to how she wants him to go to doctor appointment with him . Every time they argue is about why they didn't work or why he can't see the kids. It is so suspicious to me because why do you give her so much of your energy. Is he try to start family with me to forget what he had. Please don't get me wrong I want him to spend time with his kids. I want him and  his ex-wife to co-parent. But what I can't take is disrespect why every time y'all get around each other or every time y'all get on the phone y'all arguing why y'all didn't work out if it not about kids.