The two were first linked back in late 2014, but in 2015 Simpson told GQ Australia that they were "just mates."
"Miley is one of my best friends and she helps with some of that transitional stuff — trying to escape your childhood. She’s super open-minded and I’m working on becoming more like that," he said.
The Australian star previously dated model Gigi Hadid.
As the news of her divorce broke, Cyrus was spotted on an Italian vacation with reality TV star Kaitlynn Carter, who in turn had just split from her husband Brody Jenner. They were rumored to have been in an open marriage.
After Carter and Jenner ended their relationship, it was revealed that they were never legally married — despite having had a wedding ceremony.
Carter, 31, and Cyrus called it quits in September after just over a month of dating.