U.S. actor Brad Pitt holds his son Maddox at the starting grid before the MotoGP Italian motorcycling Grand Prix at Mugello June 1, 2008. [Agencies]

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Brad Pitt took his son Maddox go-karting on Tuesday. The 'Ocean's Thirteen' actor and his adopted son were celebrating Maddox's seventh birthday at a track in the south of France.

A source said: "It was just Maddox and Brad. Just father and son time." Brad and Maddox raced each other around the circuit several times, but it was the birthday boy who managed to cross the finishing line first.

The special outing came three weeks after Brad's partner Angelina Jolie gave birth to twins Knox Leon and Vivienne Marcheline. The couple also have adopted children Zahara, three and Pax, four, as well as naturally conceived daughter Shiloh, two.

Meanwhile, it was recently reported that Angelina is considering adopting another child. The 'Wanted' actress was so affected by footage of the recent earthquake in China she is contemplating giving a home to a child orphaned in the natural disaster.

A source said: "Angelina is devastated over the earthquake that occurred in China in May. She has been in constant touch with relief workers as part of her UN involvement, and even got her hands on photos of a few orphaned kids. "She's made overtures offering a home to one earthquake orphan, or even two if they are siblings."