Imo men tend to love the children of the women they are with, while they are with them.
This is my ex to a tee. He was desperate for us to have kids. We had multiple rounds of IVF that he funded. He jumped up and down like his team had won the cup final when they said it was twins. He spent hours with name books trying to find the perfect names.
The first few months he was all over them - fed them, changed them, got up for night feeds even when it wasn't necessary. Just the perfect dad.
Then he met someone else, decided to join the military and walked away. Didn't see them for 18 months, and even then it was only because he discovered his parents were seeing them after they approached me desperate to stay in touch with their grandchildren.
He's done the same twice more. Once to a woman he married and had three kids with. I have limited sympathy for her as she was very open about preferring him not having contact with my girls. Yet she was absolutely stunned when he did the same to her.
The last one had no idea he had any children at all until she was pregnant with their second child. He's not set eyes on their children since she kicked him out.
The only time he's interested in any of the kids now is if he has a new girlfriend and he's trying to impress. Then he's all about threatening court and wanting his rights 🙄