My first naked contact with a penis was at about 7 years old. The parents were across the street at a party and were were checked on from time to time. The other kid was 6 and he brother was five. Show me yours, etc. First, he wanted me to suck his and he sucked mine, then he called his brother who also sucked both of us and we sucked him.
First encounters at 10, we were sucking on each other within five minutes. It appears to be the natural thing to do at any age. I hope there are no longer any laws against it.