At what age, parents, did your children become genuinely funny?

I have a 17, 14, and 12 year old. I’ve really noticed that they are all becoming more and more amusing. Long gone are the endless knock-knock jokes (thank god).

My oldest son made me laugh and laugh today when I was venting about my sister (who is enormously frustrating due to her head injury). Apparently, when ever she asks him a question (one of about 8 or 10 she asks repeatedly through the day) he answers with, “Because you touch yourself at night”. I know not very appropriate but really funny. And it makes her laugh when usually the answer makes her blow up.

What were the ages of your children when you noticed they genuinely made you laugh?