Engaged to a man who has kids from the past relationship

Okay ladies I kindly need your help! Me and my fiancé have been together for 3 years. He has 2 boys from his past relationship which I have known since we started dating. I am now 7 months pregnant with his third son and this is my first. Before getting pregnant I asked him if this is what he wants and he said yes. He proposed in May last year and i found out I was pregnant in July. His first boys live in Australia with their mom and my fiancé and I live in Germany. He talks to them and goes to visit them and comes back. But whenever he goes there to visit them, he comes back sad, doesn’t want to communicate or anything of that kind. So as we were talking last year I suggested that he invites his son here (Germany) and spends time with him before the baby comes—I suggested that because I felt he was never connected to our unborn child smh and I thought he would feel much better and be ready for our unborn child and that his older son gets to find out he is going to have a baby brother. So to say…one of his boys is autistic and that’s why he stayed with his momma. His son came and now he is here with us until end January..he travelled by himself but my fiancé will travel with him back so he can as well see his second son. My concern is—things haven’t been that great lately because whenever I see them together happy and all that..I say to myself WILL HE EVER LOVE OUR CHILD the way our child deserves or? I told him how I feel and he said once the baby is here everything will be alright:)🤷🏽‍♀️ I said yoooo you think? He said yes. Remember he still pays child support for them and all that which also makes me worry sometimes. Ofcourse I like the fact that he is there for them but God knows I worry about us a lot. Now, I keep going back and forth if I should go on and marry him or not! I love him he is a great daddy to his sons and a provider but I don’t know if I am crazy or overthinking. Please, feel free to comment.🫶🏽