Scott Disick -- Having a Ball with Rob Kardashian

After what looks like one too many bloody marys, Scott Disick was caught sleeping with a Kardashian other than his baby mama Kourtney ... her brother Rob Kardashian.

Kim Kardashian tweeted this adorable pic of Scott cuddled up with his head nestled up against Rob's comfy crotch at the airport ... not that there's anything wrong with that.

The Kardashians really do like to keep it in the family.