Britney 'seething' with K-Fed girlfriend

Britney Spears is reportedly 'seething' with Kevin Federline after he allowed his new girlfriend to get closer to their children.

The singer is said to be unhappy that professional volleyball player Victoria Prince has taken on the role of 'stepmum'.

"Victoria and Kevin went on a trip to some of K-Fed's family and took the kids with them," a source told heat.

"Victoria and Kevin have only been dating for a couple of months, but she's pretty close to the boys already and is a natural with the kids.

"They feel comfortable around her. She was very much the doting stepmum and got involved with looking after them and carrying them around, soothing them when they cried, stuff like that."

Spears recenty threatened to cancel her upcoming world tour if her children could not accompany her.