DEMI MOORE is dating a 27-year-old rock drummer named Sean Friday.  And they recently went to Mexico with Demi's daughter RUMER and her boyfriend, actor Jayson Blair.  It was actually Rumer who set them up.


Well, this is interesting:  Blair turns 30 in March . . . which means that Rumer's boyfriend is OLDER than her mom's current slice of guy.  And at 51, Demi is four years older than her new boyfriend's MOTHER.  (If anybody's keeping track, Rumer is 25.)