Kevin Federline is seeking primary custody of his and Britney Spears' children.
Kevin's lawyer Mark Vincent Kaplan filed the order at the Los Angeles Superior Court yesterday.
The 28-year-old is hoping he can show cause for being awarded primary physical custody following Britney's recent erratic behaviour.
A sourcetold People magazine: "Kevin is worried Britney is exposing the boys to unnecessary risk. His lawyer hopes to get Kevin primary custody."
Kevin and Britney, whose divorce was finalised less than two weeks ago, originally agreed to equally share custody of 22-month-old Sean Preston and 10-month-old Jayden James.
However, Kevin was reportedly reluctant to sign the divorce settlement papers over growing concerns for the singer.
Britney, who entered Malibu's Promises rehab centre earlier this year, has been a regular fixture on the party scene.
She also allegedly enjoyed a naked romp in a hotel swimming pool - just hours after breaking down in tears while shooting the promo for her comeback single Get Back.
The 25-year-old singer shocked onlookers by downing cocktails before baring her breasts, diving into the pool and simulating sex with an extra from the video at Los Angeles' Standard Hotel.
Britney filed for divorce on November 7, 2006, after just two years of marriage, citing "irreconcilable differences".
