Who's the Kim Kardashian of the Gronkowski family?!
IT'S NOT ROB!
This according to the NFL superstar himself who says he's teaming up with his bros for new FAMILY project ... and it sounds insane!
Rob tells TMZ Sports he spent his entire offseason beating up his brothers -- Gordie, Dan, Chris and Glenn -- for their new YouTube channel, "The Gronks."
"We all just compete verse each other," Rob says ... "We all team up with each other to do all different type of weird activities or fun activities, or crazy activities, however you wanna categorize it.