It's now believed they may have called it quits as early as June. The last public footage of them together was on July 9.
The source claims Cyrus and Carter have been friends for years and are now "seeing each other with no labels attached."
A statement released on Sunday said Cyrus and Hemsworth had "agreed to separate at this time" after deciding "this is what's best while they both focus on themselves and careers".
"They still remain dedicated parents to all of their animals they share while lovingly taking this time apart. Please respect their process and privacy."
Hemsworth recently confirmed his and Miley's split, and insisted he wouldn't be speaking about the matter any further.
He wrote on Instagram: "Hi all. Just a quick note to say that Miley and I have recently separated and I wish her nothing but health and happiness going forward.
This is a private matter and I have not made, nor will I be making, any comments to any journalists or media outlets. Any reported quotes attributed to me are false.
Peace and Love."