Kelly Osbourne and Sid Wilson quietly hit the brakes on their engagement more than a month ago ... and while they're not together right now, TMZ has learned the door might not be fully shut.

Sources with direct knowledge tell us the split actually happened weeks ago, but it's only surfacing now. We're told Kelly and Sid have always had a bit of a hot-and-cold dynamic, and that pattern played into where things stand right now. Our sources say while they're currently apart ... there's still a possibility they could reconcile.

It's still unclear exactly what caused the breakup.

As Daily Mail reported ... the split came during an "incredibly difficult" period for Kelly following the July 2025 death of her father, Ozzy Osbourne. The outlet's source said the pair tried to make things work, especially for the sake of their child, but ultimately decided to go their separate ways.

Sid proposed just seven months ago during Ozzy's final Black Sabbath concert, making the breakup feel especially sudden. Kelly and Sid were friends for decades after first connecting when Slipknot toured Ozzfest, the festival founded by Ozzy and Sharon Osbourne.