The number one you're in a toxic relationship is when your significant other causes a rift between you and a family member. In Usher's case, his older, possibly pregnant fiancee, Tameka Foster, is rumored to be behind a plot to fire the singer's mom/manager.

"They definitely don't get along," one spy tells us. "Tameka came to Jonetta's birthday on April 6. They hugged and posed for photos, but it was all for the cameras."

The rift dates back to when Jonetta encouraged Usher to fire Tameka as his stylist. "Tameka went on the radio and took some shots at Jonetta," says a source.

But Usher, 28, still liked Tameka, 38, and vice versa. In fact, she ended up leaving her husband for him. (Reps are denying she's pregnant.)

"Tameka has a hold over him," says one friend. "Nobody can figure it out. Some people think he may make Tameka his manager."

Execs at Jive, Usher's label, are said to be concerned. "They think Jonetta's done an incredible job with his career. They're encouraging her to take on Britney Spears."

I'm rolling my eyes at the Britney Spears thing. Why does every parent/manager want to work with this girl. First Joe Simpson, now Usher's mom. The next thing you know Matthew Knowles is going to try to sign her. The girl doesn't need a new mom or dad, she needs a therapist. But, uh, I digress. Back to Usher and Tameka — he had better assert himself real quick before his career goes down the drain like the aforementioned Spears.

[NYDN]