When i introduce a new young male with my males is during breeding. When i move females in with the males, i also move a new male in with the older males. This actually gets the males aware of him but not worried hes there due to females are around.

Never had a single fight to the younger ones. They wrestle with him all the time now.

Heres the new male i held back and introduced this past weekend. Hes about 100g and other 2 males are 500+g