According to Access Hollywood, a source revealed Rossdale left Stefani in hospital after she had given birth to son Apollo in February last year, just so he could have sex with Mann.
It follows reports that Rossdale had a three-year affair with the family’s longtime nanny, causing Stefani to end their marriage in a split, which the singer has described as “unexpected”.
The source also claimed that Mann would bring the couple’s children to visit Rossdale while he was on tour and they would allegedly have sex on the tour bus while the kids slept, all while Stefani was in Los Angeles fulfilling her duties as a judge on The Voice.
Stefani and Rossdale have three sons, Kingston, 9, Zuma, 7, and Apollo, 20 months.
Stefani was said to have discovered the affair in February after she discovered explicit texts between Rossdale and the nanny — including nude photos of Mann and their plans to meet up for sex — on the family’s iPad.
“Everybody knows that my life blew up last February. I’d just been dealing with that. Unexpected. I was going along thinking that was going to be the rest of my life and it’s not. I don’t know what happened,” she said in an interview on KIIS FM.
Mann joined the family as a temporary nanny in 2009. She was soon made permanent and Stefani is said to have treated her like a sister — letting her borrow clothes and trusting her with the children.
US Weekly reports that the affair had been going on for three years before Stefani found out.
Since the split, Stefani has begun dating fellow Voice coach Blake Shelton, which has been confirmed by the singer’s rep.