Photojournalist Doug Pitt, who is three years younger than Brad, will be seen in the new advertisement for Richard Branson's Virgin Mobile company in Australia.
In the ad, Doug invites viewers into his modest suburban home to give them an insight into how the "second most famous Pitt lives".
The voiceover says, "While his brother lives the life of a Hollywood A-lister, Doug's life is a little different. Virgin Mobile believe in a fair go for all and want to give Doug a taste of his brother's lifestyle, starting with his first ever celebrity endorsement."