Harvest moon 64 how to have a baby?

Get a pink heart with a girl. After that, eventually there will be a blue feather at Ricks shop. Buy it, and give it to the girl. That will be proposing to her. After you're married, give things she likes to her everyday and talk to her. She will start saying either she feels sick, or that shes pregnant. It takes 30 days to have the baby.