Kevin Federline held an early birthday party for his sons while their mother, Britney Spears, was performing at the MTV Video Music Awards at the weekend.

The bash was held at Federline's house in California on Sunday, while Spears made her comeback performance in Las Vegas, which has since been panned by critics.

Spears' father Jamie and her mother Lynne were both present at the party, where 20 guests used the aspiring rapper's swimming pool.

Assistants for Federline were spotted buying cakes and balloons for Jayden James, who turns one tomorrow, and Sean Preston, who will be two years old on Friday.

Both Spears and Federline are currently in the middle of a custody battle over their children after K-Fed filed for primary custody last month, following the finalisation of their divorce.