The trick to boosting your population is to up your house building. I know it seems counter productive but you probably have loads of adults who are capable of having children but won't until they move out of their parents' house and in with a partner.
Also hunters and gatherers are a million times more productive than farmers.
Yea I built a couple more houses last night and instantly 3 kids were born
Make sure you don't build houses too quickly, though. Kids eat but don't produce, so too many of them will stretch your food production.