R.A.
My son is 13, but when he was 9 I talked to him about puberty and how his body will go through changes, and hormones,etc.. he isn't a boy that enjoys discussing body parts or medical stuff( he gags and gets grossed out), so I discuss this in stages with him. He will come to me about different things, and he calls it " the changes" because he hates the word puberty, lol. Anyways, it's important to keep an open dialogue and to allow him time to explore and discuss if he wants. I would also give him books to read on his own if he is embarrassed to talk about it.
His voice is cracking now, and he has facial hair- stuff he know understands is part of the process..
But it's important to discuss this now with him, so he has somewhat of an idea of what will start or what is normal.