yard cousin

Deep South reference that recently made news that refer to persons which, due to their level of upbringing, you may invite over for family events but certainly don't allow into your own home. They may or may not be related to you by blood or marriage.

From the Chicago Tribune (4/28/13) - in reference to societal culture in Tupelo, Mississippi :

With new arrest, ricin case takes a strange turn.

That shocks no one here. "Tupelo is a kaleidoscope," said sociologist Mark Franks, who grew up in nearby Booneville. There are true geniuses walking the streets of Tupelo, he said, and incredibly wealthy, generous people. But also, "every wall-eyed uncle and 'yard cousin' — just referencing the local pejorative — makes it into Tupelo, Miss. It creates a peculiar culture."

chicagotribune.com/news/sns-la-na-tupelo-arrest-20130428,0,1023280.story