Rob Kardashian -- Bails on Kimye Wedding After Major Family Clash

Rob Kardashian left Florence, Italy BEFORE his sister Kim got married to Kanye West ... and we're told it's because some major family drama went down.

Rob booked a flight from Florence to L.A late last night in a hurry ... and we're told he was in tears while desperately trying to secure a seat.

It's unclear what caused the Kardashian family beef -- but it had to be bad -- considering he missed out on not only his sisters wedding ... but one of the biggest celebrity events of the year.

We just shot Rob leaving LAX and he was clearly not in a talking mood.