This happened when my friend, (we'll call him Dave) and I were about ten. (Well, I had recently turned ten, and he was a few months away.) We'd just entered puberty, and the constant tents in our shorts whenever some hot X'er was on TV were proof.
Anyway, we were watching some beach movie at his house while his parents were gone, and I said 'Would you look at those things!' Dave said 'Are they real?' 'As real as our chances with her.' After about ten more such bimbos, I said, 'I have to use the bathroom.' 'You're going to jack off, aren't you?' 'Okay, you caught me.'
'Well, I need to do the same thing.' So we played rock-paper-scissors to see who could go first. We tied about a half-dozen times and then I said 'Hey, we're both guys.'
So we both pulled them out and stroked. We lasted about four minutes. (Ten years old, remember?)
We continued doing that into our teens. We even did each other several times.