There are several posts about late puberty and small penises.
Allow me to comment. I have 2 boys and three girls. Only one of the boys and one of the girls entered puberty by 10. The rest were about 14 - 17.
Because we are casual about nudity at home, it's easy for me to see how the kids are maturing. Their mental and intellectual maturity has always been advanced. Because their mom and I keep our pubic hair shaved all the time, our kids never realized that pubic hair appearing was a cool thing or important. All the females in our household are small breasted, so having C cups wasn't a real sign of maturity either; in fact, my wife and none of the girls wear bras much; there's not much to hold up.
None of our kids worried about bigger penises (although the boys do have large penises, aroused and flacid) and the girls weren't worried about big boobs and big clits.
Our nudity at home has made discussions of sex easier and casual. Our kids have seen erections and understand what causes them. They knwo the physical signs of female arousal, because they've seen their mother's and sisters nipples get hard and bigger and they've seen their mom's and sisters' clitorises engorge and theirr vaginal fluids when they're aroused.
I understand that all this casual sex talk at home is unusual, but at makes the whole issue of puberty and sex non-issues.