Brad Pitt won't marry Angelina Jolie because he fears getting divorced again.

Actors Brad Pitt and Angelina Jolie arrive for the New York Film Festival premiere of "Changeling" in New York October 4, 2008.[Agencies]

The 'Burn After Reading' star - who split from former wife Jennifer Aniston in 2005, shortly before he began his relationship with the 'Tomb Raider' star - was reportedly left traumatised by the breakdown of his marriage and is refusing to walk down the aisle a second time.

A source told Life and Style Weekly magazine: "Brad's divorce from Jennifer was painful. It was hard on his parents and he considers it a major failure in his life.

"His big excuse for not marrying Angelina is that he hates even the possibility of something like that happening again."

Angelina recently revealed their six children have begun asking why they have not yet married.

She said: "Sooner or later it will be the kids who ask us to get married. You know, they see films and start asking questions. Such as, 'Why are Shrek and his love Fiona married and you're not?'"

Meanwhile, the couple have reportedly hired six nannies and several cars to help them cope with their large family while Brad is filming 'Inglourious B******s' in Germany.

Mya Walters, a public relations manager for car company Volkswagen, revealed: "We've provided them with more than 20 Volkswagens while they're here in Berlin."

During a recent trip to New Orleans, the couple - who raise three adopted children, a biological two-year-old daughter and three-month-old twins together - originally flew out with four nannies but had to jet in an extra two after reportedly struggling to manage their large brood.