N.M.
be glad he is asking that way you can teach him right way and he not learn it somewhere else the wrong way, just find a way to explain it at his level enough to do at that time he doesn't need to know all of it just some of it enough goe his level, don't lie to him it will haunt you there are way to explain things at his age it is part of growing up. My oldest daughter was real up set at 17 months old when she discovered she got cheated on body parts down below and I just explained she had girl parts and he had boy parts that was enough, she was crying but after I explained it she was fine. But my mother lead me to believe that the stork brought babies boy was I in for a shock. but lots of kids now days don't come to the parents they go else where or the parents don't think they are old enough to know anything, bad idea when you child ask they need answers and they need they can come to you for them that way if someone tells them something different they will ask if the other person is right you would be shocked at what some kids know at age 8 good luck