Nikki Sixx and Denise Richards Call It Quits

After a few weeks of casual dating, Denise Richards and rocker Nikki Sixx have gone their separate ways.

UsMagazine.com first broke the news that Charlie Sheen's ex, 39, began quietly dating the Mötley Crüe bassist, 52, in December.

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"They have a lot in common and are taking things slowly," a source close to the pair told Us at the time of Richards and Sixx, who have been neighbors for years.

After news of a split surfaced late Saturday, a Richards insider confirmed her romance with the rocker was never that serious to begin with.

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"It's crazy how this is being made out to be some big breakup. They were never exclusive or serious to begin with!" the insider tells Us. "I could count on my hand how many times they went out.

"They decided to try it and she was not interested," continues the source. "That's dating! This isn't some big, dramatic split."

A rep for the actress had no comment.