I would be interseted to know why they do it too?
Is it because one of them has a motherly instinct?

I have five males and a female. Of the males, two engage in this
behavior. Well, one does, and the other tolerates it. Up to a point.
Rascal approaches Weasel and begins licking him about the face. Weasel
seems to enjoy it, but then starts to pull away. Rascal then wraps a
paw around Weasel's neck and forces him to endure more. Weasel objects
strenuously, wrestling match ensues.