Britney Spears Shirtless 'Uncle' Post Confuses Fans, Man Is Not a Family Member

Britney Spears' bizarre social media post about her shirtless "uncle" isn't actually one of her actual relatives ... but the guy in the pic is super close to the singer, and we know who he is.

Here's the deal ... Britney posted a strange photo on Instagram Tuesday night of a shirtless man taking a mirror selfie, which she captioned ... "This is my uncle 😉 !!! What if his back is my face 🤔🤔 ???"

Britney fans were left wondering who the hell the "uncle" is -- his face is out of the frame -- and what the hell Britney was talking about.

Sources with direct knowledge tell TMZ ... the guy in Britney's post isn't her uncle, it's her longtime manager and best friend Cade Hudson.

We're told Britney posted an old photo of Cade from a few years ago, and there's no real meaning behind her post ... basically, she was just being silly and having fun with her followers.

For the record, here's Britney's real uncle, Willie Spears ... who bears no resemblance to Cade.