Josh Duggar -- Cracks Molestation Joke ... Dating Family Is What We Do! (VIDEO)

Josh Duggar is from Arkansas ... so it's totally cool if he dates his siblings.

Back in 2008 -- long before Duggar's molestation past came to light -- he made a quip during an episode of what was then called "17 Kids and Counting."

Josh describes a double date scenario with his then-fiancée Anna ... he ended up going with 2 of his siblings.

Josh explains, "We chose Jana and John David. We thought why not, have a double date ... We are from Arkansas!"

He then broke out in laughter.

Not so funny now ...