"His friends are telling people it's over," according to an Us Weekly source.
Another source said the split had been looming on the horizon for the couple for some time.
"They have been moving in different directions for a while," the source said.
Dupri, who was noticeable absent from Michael Jackson's memorial last week, produced several of Janet's recent tracks on her last two albums – which could have contributed to the split, according to the mag.
"You shouldn't mix business with pleasure," a friend of the former couple told the mag. "Janet felt their lives were too crossed and they should have kept things separate."
In addition to her break-up, another source said Janet is still in the midst of mourning for her brother.
"She's devastated," another insider said. "She's busy caring for Michael's kids. Janet's the family's backbone."
Janet was previously married to Rene Elizondo. They divorced in 2000.
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