It's normal. Chins hump one another to establish dominance. Just make sure he isn't doing it too excessively and stressing the other chin out, and make sure there are no other aggressive behaviors going on.
Not to insult your intelligence, but are you sure you have 2 males? I thought I was given 2 males by my breeder and 1 started to hump the other (I thought it was dominance, till I checked their sexes)...now I have 3 babies haha. Someone once told me to get a chin safe, stuffed animal and place it in the cage with him and that way he might go after the stuffed one and not his cage mate