Babies!!!!!!

My boyfriend and I have been together for 2 years and couple months. We have our own home, and each have a decent job. I really want to have a baby, but I'm not sure how he'll react when I sit down and talk to him about this serious topic. We've joking talked about it, but every time I bring it up now, he thinks it's a joking matter. How do I tell him I'm serious about us starting a family?