How young us to young?

My boyfriend and I are so happy together and can't wait till we get married. We really wanna have a baby together but my question to you is how young is to young?? It's kind of a complicated situation. He had a daughter for two years with his now ex wife. Well they did a paternity test and found out she wasn't his. It broke his heart. Him and I both really wanna have a baby. We are both financially stable. I just don't know... Please help??