Britney Spears has left fans shocked after sharing a picture of her sons as she admits she has seen them "grow up so fast." The 39 year old is mum to Sean, 15, and Jayden, 14, from her marriage to Kevin Federline, which broke down in 2007, just one year after Jayden's birth. She took to Instagram on Tuesday morning to share an image of herself beaming as she stands in between the teens as they enjoy a walk through a field.