thanks for all of the great replies.
Max is 9 months old and Milo is a little over 6 months. (they are half brothers with the same father.) Milo is bigger than Max and much more aggressive. He insists upon humping Max until his little "red rocket" appears, which isn't so little. I've got to say the first time that happened i was so grossed out. (i have only had female dogs up until now).
Anyway, I am hoping neutering will stop Milo from doing this. My 7-yo daughter is questioning the whole thing
