The NSYNC star took part in Ancestry's 2 Lies & a Leaf alongside husband Michael Turchin, during which he discovered that Britney is his sixth cousin once removed.
"Look, I wanted to be related to the Queen (of England) but now I'm related to the Queen of Pop," he laughed, before adding, "That is so crazy, though, because I feel like she's my little sister. And this whole time she's been my little cousin."
The 34-year-old, who found success with his boyband around the same time Britney went from unknown singer to worldwide phenomenon, continued to admit he's always felt a bond stronger than just friendship with the "Toxic" star.
"For some reason, I always felt like we looked like family when we were kids," he said. "This means so much to me. She is like family to me. So, the fact that we are blood-related is amazing."
Britney has yet to publicly respond to Lance's relative revelation.
Lance Bass previously said he hadn't been in touch with Britney for years.
But he contacted her sister Jamie Lynn Spears regarding the conservatorship when #FreeBritney movement first gained public attention. He assured fans that everything was alright with Britney. "I have talked to Jamie Lynn recently, which is why I feel so much better about this situation," he said. "They aren't as worried as we are."
He added in another occasion, "I do trust her sister, Jamie Lynn and as long as Jamie Lynn is cool with whatever she's doing, I mean, I have to be."
As scrutiny over Britney's conservatorship intensified, he changed his tune and agreed that Britney looked "sane enough to pick her own people."