Humping is NOT NOT NOT a "sexuality" thing at all (and honestly you will heartily offend a good many people saying it is!) It's dominance, pure and simple. Any dog that 'humps' another dog is merely trying to be dominant. It may happen within any sex (m/m, m/f, or f/f, or f/m) and it can occur with dogs that are intact or not, it's simply that dog's way of saying "I'm boss over you".
Occasionally a dog will help mentor or 'parent' another dog lower in pack status, but even that is rare because they just don't view sexualty or "parenting" as we do. The dominant male/female in a pack may work together to help protect junior or lesser pack members but you can't jump to human roles and assume something like that -- a dog that isn't targeted for humping - either that dog is already being submissive or he may respect that dog's position in the pack.