When did your child start talking?

I wouldn't care what they say or how they feel children hit their milestones at different times sometimes on, early or late my son is 18 months he sings and talks when he wants but he doesn't say whole sentences yet am I worried? Not one bit because he understands EVERYTHING I say boys develop slower than girls sometimes my niece didn't start talking until she was 2. If the pediatrician isn't worried than I wouldn't worry if you read up on the monthly milestones they'll tell you a lot so I would just ignore the negative comments.