Am I being selfish?

I am a single/ unattached 29yr old and I started dating this girl that has two children (ages 4 & 6) from two different guys. It’s not really a big deal that she has kids, but she says she doesn’t want any more children and I have always wanted to be a father. I know that I would be a great stepdad and I’m sure her kids would look up to me as a father, but its not the same as having my own.

Im going to talk to her this weekend about it and hopefully she is not definite about her decision to never have kids, but I think this could be the make or break moment.