Help - he won't have kids with me, what do I do

My guy has three kids from his previous marriage and knows how important it is to me to have a family. 

But because he feels like he isn't the best father to his 3, he won't have a family with me. Absolutely refuses.

I want to be with him like you cannot believe. He is my other half. We are right for each other in every way, except he cannot see how I feel on this matter. 

I have tried to explain to him that I am not his ex, that it will be different, and that this means more to me than anything. I have explained how his kids do not see me as any sort of mother figure and hate me. I have explained that I want a piece of him if something were to happen to him. I have  explained that, as I just watched my grandfather die, I do not want to go through that alone and if I do not have any children and he isn't there, then I will. I want more than just a husband or step children. I want a family. 

Has anyone been in this situation and been able to convince their significant other of how they feel? Or am I just prolonging the inevitable with having to one day leave him.