I don't have any kids, but I did have the talk with my little 13 year old brother in-law. I know that his mom will not give him any kind of a talk because she didn't even tell her two older daughters what to expect when they got their periods. My wife said that she thought she was going to die when it happened. I think that my mother in-law would kill me because she makes him wear one of those purity rings and goes to all of the weird purity events with him. He already knows stuff, so you might as well tell him how to protect himself if he so feels like doing something one day.
Neither of my parents had any kind of talk with me, which is kind of nice because it would have been pretty ackword. The closest thing to a sex talk they had with me was when they found a box of condums under my bed when I was 15. They went ballistic on me so I told them that I would take the box that wasn't opened back to the store that I got them at. After I took them back they asked if I was still going to be having sex, so I told them yes, just without protection for now on.