Hello @hopeful5141 and welcome to Fluther!
You don’t say how old his kids are (unless it is somewhere and I missed it), but assuming they are in their upper teens, the natural course of things is for him to start the process of letting go of his kids and letting them grow up. At this point it sounds like he might have a co-dependent relationship with them which is not healthy for anyone.
My husband was a single father to his three children who were all grown up (20, 22, 24) by the time we met. Because of his and their situations, he was very dedicated to his children and had made it clear to every woman he had dated to that point that his kids came first. Period. He definitely had the feeling that when he was with me, he was taking from his children. Slowly but surely and with the help of an awesome therapist (single and couples therapy), he renegotiated his relationships with his kids. They are thriving, going out on their own and starting their lives. It was challenging for both of us and for his kids but it has turned out great for all involved. He had to set his boundaries and stand by them. The key for us was that he knew it was time to do this and even though it was tough he forced himself. I think that is going to have to be the key for your man, he has to decide that renegotiating his relationship with the kids is what is best for all involved then he has to commit to doing so.
There wasn’t much love in my first marriage, and like your husband, I found myself giving all of my affection to my kids. Since I have remarried I have had to get over the feeling that when I am loving my husband I am taking love away from my kids. It took me a while to understand that modeling a loving healthy grown-up relationship for them is not only not hurting them, it is a gift. It took some time for me to understand that but I finally got there and I know my marriage is healthier for it and my kids are lucky to see true love in action every single day.
So my advice is talk to him, just keep talking and communicating. See a therapist to help navigate the changes. Stay dedicated to each other, present a united front to the kids, keep working and you’ll get through this. Good luck to you.