Is it okay for a 2 year old to have 8 teeth?

I've read that most kids get 20 teeth by age 2. My son has four teeth on top and four teeth on bottom. I think it's a genetic thing, but since I can't remember how many teeth my siblings had at his age I was wondering if it is okay? All my family have had baby teeth into our early twenties (and thank God that's the only teeth issues we've had). So is it safe to assume that if they come in slowly it's normal since they come out so slow as well? Or should I get in touch with his doctor?