Chris Rock's younger brother wants to do more than slap Will Smith ... he wants to lace up the gloves and climb into the ring for a boxing match!!!
CR's brother, Kenny, just signed a deal with Celebrity Boxing founder Damon Feldman for a fight this summer down in Florida ... but he doesn't have an opponent yet, and he's calling out Will.
Kenny says the size difference wouldn't be an issue for him ... even though Will's taller and once played Muhammad Ali on the big screen .