LeBron James -- MY KIDS CAN DUNK HARD .... Just Like Blake Griffin!!!

Apparently, MONSTER DUNK SKILLS run in the family ... 'cause LeBron James' kids just went HAM on their Nerf hoop ... and the rim-crushing highlight was all captured on video.

LeBron's sons -- 6-year-old Bryce and 9-year-old Bronny -- teamed for a crazy alley-oop style slam on Christmas morning ... and LeBron was so proud, he posted the footage online.

James even Instagram'd a message to L.A. Clippers stars Blake Griffin and Chris Paul ... saying, "Bronny and Bryce gone hold down Lob City until y'all get back. Cool? It's like the both of y'all but we gone keep it in our room. Haha."

Fun Fact -- If 28-year-old LeBron can stay healthy enough to play in the league for 10 more years, he's got a shot at playing ALONGSIDE his son.