Tony Curtis & Sean Connery's Grandsons Tagged In Graffiti Crime

The grandsons of Sean Connery and Tony Curtis are giving their family names a bad rap ... because cops say they snuck onto someone's property and egged on a tagger.

Law enforcement sources tell us the young adult grandsons were caught on tape last month jumping a wall with a teenager and watched the guy tag a wall and garage door. We're told LAPD hunted down the trio and the juvenile fessed up.

Law enforcement tells us ... cops are sending the case to the L.A. City Attorney for possible prosecution for criminal trespass.