My oldest son is 8 and my younger son is 6. While they both have shown normal physical development, the 6 year old's penis is very large in contrast to the 8 year old's penis. In fact, my 8 year old's penis seems to look like an acorn for lack of a better explanation. We have never mentioned it to him but I think he is noticing the difference between him and his brother and is starting to feel self conscious about it. Is this normal or is something wrong? If so, how can we help?