UFC's Michael Bisping -- Son Challenges Father ... Let's Rumble!! (VIDEO)

Forget Luke Rockhold, Michael Bisping had ANOTHER challenger waiting for him when he got home Wednesday night -- his 15-year-old son ... who threw down with dad right in the middle of their house.

Turns out, Callum Bisping is a high school wrestler -- a pretty good one -- and he tried to test his skills against the UFC middleweight champ.

Check out the clip ... not bad for a 15-year-old. Even Michael admits his days as the alpha male in the house are numbered.