Briteny Spears has shared a rare picture with her teenage sons, Sean Preston and Jayden, and said "it's very hard for any mama especially a mama with boys seeing them grow up so fast".

Spears shared the picture on Instagram and explained to her followers that she doesn't usually post pictures of her "boys" because "they are at an age where they want to express their own identities". 

The popstar shares her children, 15-year-old Sean and 14-year-old Jayden with ex-husband Kevin Federline. 

Spears wrote: "It's so crazy how time flies .... My boys are so big now!!!! I know … I know … it’s very hard for any mama especially a mama with boys seeing them grow up so fast !!!! Talk about enough to make you go to your knees ... GEEZ!!!!

Spears posted two versions of the same picture. The original showed her and her masked sons posing in a field, while an altered snap had a dramatic sky as a background.

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She added: "I’m extremely lucky because my two babies are such gentleman and so kind that I must have done something right!!!! I haven’t posted pictures of them for some time cause they’re at the age where they want to express their own identities and I totally get it .... But I went out of my way to make this cool edit and guess what .... They’re finally letting me post it !!!

"Now I don’t feel left out anymore and I’m gonna go celebrate .... Oh s*** I guess cool moms don’t do that ... Ok I’ll just read a book instead !!!!

Spears is currently locked in a legal row with her father, Jamie, who has overseen her estate since 2008. She has said she will not return to the stage while he holds the role as conservator. Lawyers for Jamie argue his handling of her affairs saved her from financial ruin.

A hearing in the case is set to take place in Los Angeles on March 17.