TTC baby #1. My man's #3.

Im 29, he is 36. We've been together for 10 years. He had his first kid at 16 and the second at 19. His son is 20 and daughter 17. I decided to wait on getting pregnant until both his kids where 18. I don't want his kids to feel he stopped raising them to start rasing new kids. His kids don't like me and I know they will be mad at him when he tells them he's having a baby with me. He does want to have 2 kids with me but just knows his kids will stop talking to him. Do you think they'll be in love with the baby when born or are there kids that will never accept?