KEVIN FEDERLINE's ex-girlfriend Shar Jackson has dubbed the star's recent weight gain "daddy weight" - putting it down to him gaining full custody of his kids with ex-wife Britney Spears. Federline was granted full physical custody of two-year-old Sean Preston and one-year-old Jayden James last year (07) after Spears failed to adhere to court-ordered medical tests. The troubled singer was also stripped of her visitation rights to the boys in January (08) but the former couple has since agreed a new deal to let Spears have limited access to her children. Federline has embraced his role as a full time father but has been spotted looking noticeably fuller-figured recently. And Jackson blames his weight gain on spending more time at home with his sons. She tells Us magazine, "It's daddy weight! When you are a full time parent, sometimes you can't focus on you. If gaining a few pounds is your only problem, life's not too bad!" Federline's representative has also confirmed the 29-year-old is not bothered about piling on the pounds, saying, "He's a stay-at-home dad, and people tend to gain weight when they are home with the kids. He's very happy with the way he looks."