The melee that erupted around Kylie Jenner - between a defensive grandfather and photogs - was fueled by alcohol … according to the grandpa's family.
We spoke to the mother of one of the 3 girls who were waiting for Kylie outside The Nice Guy Saturday night … when the girls' grandfather opened a can of whoopass on the paps.
Sporting overalls and a cig hanging out of his mouth - gramps looked like he was straight out of central casting, but his daughter says the fight wasn't an attempt to grab the spotlight … it's just that he was drunk.
The mother, who wants to remain anonymous, tells us grandpa had a few drinks before going out, and then some more at a bar in Hollywood. She says the family had gone to The Nice Guy specifically to see KJ, because her 11-year-old daughter and her 2 friends are obsessed.
She says the girls are now grounded from following Kylie because she doesn't want people thinking they're stalkers. As for grandpa - she insists he's normally a “warm, caring man.”
He was NOT grounded.