United Kingdom, Oct. 24 -- Britney Spears' sons are "afraid she is going to die", their dad has claimed.

The Toxic singer had been rebuilding her relationship with Sean Preston, 20, and Jayden, 19, over the last year but her ex-husband Kevin Federline has revealed the boys have now distanced themselves from her again and are "terrified" that something bad could happen to their mom.

Speaking on Piers Morgan Uncensored, Kevin said: "[Britney] saw one of my sons one day this year, and he decided not to go back over there because of what he saw.

"The other one, Jayden, who's my younger son, is 19 now. He's been over there quite a few times over the past year, and he's stopped seeing her in the last few months because of the situation.

"An...