I have a version 4 and a version 3, i tried connecting them when they were adults but were still too young, so the next day when they were both 5 years old i connected them and they had tamababies, so you have to wait until they're both 5, and for the matchmaker to come you have to wait until it's 6.
Hope that answered your question of how to mate them
HAppens usually when the matchmaker comes. She Usually comes when your age (on your tama) is about 6-8 something like that... anyway, you have to be atleast more or atleast be 72 hours of being an adult.