Hi K.. Responding to your post, I noticed that you said that your 8 1/2 son asked you about his testicles, not where do babies come from. Just like any other part of our bodies, testicles have a function and it should be explained just like any other part of the body. Go to the library or the internet and search information about testicles with illustrations that explains exactly why boys and men need testicle. If then he asks about sexual relations, don't hold back without been explicit. Unfortunately, kids now a day are exposed to the wrong information about sex thru TV, movies and music. Also, kids talk among eachother about sex and if at this age they have not been explained about the purpose of sexual relations and the proper way of going about it, they will experiment. I have 2 girls age 14 and 11 and my husband and I have been having conversation about sex, marriage, dating, consequenses, etc with them from an early age (of course, explanations were according to their age) We have never treated the subject of sex as a secret. Another advice, don't wait until they come to you and ask, initiate the conversation. Doing it like that, will avoid your son going to peers or other sources to get the wrong information. We are Christians and God's Word the Bible as well as Bible based publication about the subject has helped us. I'm be very happy to share, let me know.