Best definition
Weird Uncle
That creepy bastard who never got married and scares the shit out of other family members. He usually has a

unibrow, 1970s style big glasses, a toupee, and is really short. Often seduces young children and makes movies of the experience in his basement. Also known as the black Sheep in some cases

When I was but a wee lad, my Weird Uncle Andre took me to a baseball game. Then he took me home and made a video of me naked with a monkey in his basement. I rather enjoyed it then, but now I’m as scared as hell of that sick bastard…well, at least I was before he got sent to prison and gangbanged.