A.K.
I have an 8 yo boy too, and I have kept any talks, very vague, and only if he asks about them - I see no reason to tell him any in depth stuff at this age. I think it is more important for girls to know because they develop a bit younger than boys.
He knows about menstruation, because he sees the stuff and asks what it is, so I explained about the womb lining building up for the baby, then coming out each month if it is not needed. That grossed him out for a while.
We have chickens, and a rooster, and they mate A LOT lol, so he knows something is going on, I explained it very simply that when the rooster goes on the hens back, it fertilizes the egg, and a baby will grow - and that is the extent of "talks" so far.
He knows a baby grows in the womb, and comes out of the vagina, because I had a 3 yo, but he doesn't know any mechanics, of how that happened!