vasectomy

so my soon to be husband has 3 children 11,7, and 5. he had a vasectomy after his youngest was born because he thought he and his wife were done having kids. but, years later here we are we are getting married and i have always wanted a child. I lovw his kids as if they are my own however they aren't and I have to accept that but what im asking for is some advice.

is it wrong for me to ask him to get a reversal done? we have talked about it before and he said he woukd get it done but i dont rhink he really wants to do it and every time I bring it up we start fighting. .... thoughts???