Brad Pitt proposed to Angelina Jolie over fear that her life is at risk

Washington, May 16 (ANI): Brad Pitt and Angelina Jolie, who are the parents of six adopted and biological children, decided to get married because of the actress' work with the United Nations.

Apparently the couple feared Jolie may not survive a dangerous new mission with the UN helping to battle drug lords.

The 36-year-old, who is a goodwill ambassador for the UNHCR refugee organisation, will be involved when the UN launches a fresh war on South American crime bosses.

"Brad's terrified something bad will happen to her. It's why he wanted to cement things with a wedding," Contactmusic quoted a source as telling the Sun.

Earlier this year, she wrote a farewell letter to her fiance after becoming scared for her life on a UN mission.

"'I wrote a note to Brad and figured if anything happens he'll find it," Jolie said.

"'They gave me a briefing and they said everybody needs to write down their blood type," she said.

The Hollywood A-list couple, who met on the set of 'Mr and Mrs Smith' in 2005, have kids Knox, Vivienne, Pax, Shiloh, Zahara and Maddox together, and announced their plans for a wedding last month. (ANI)