Let me think here. He's in high school, so his age is like...15-18? I know Japanese high school only has three years, but I can't remember when those three years start, so it's just an estimate.
As for the kid...fuck, how am I supposed to tell? I don't spend a lot of time around little kids. I'd guess, I don't know...4? 6, at the most. I'm using my own childhood as a basis, but I had an odd childhood, so I might be a bit off there. I remember bathing with my dad when I was that young, I think.
I was going to get to a point, but I realized this conversation to come to two different conclusions. Ahhhh, I guess it comes down to personal views. As for me, I can't sexualize it, even if I try.