During a recent family outing to Toys "R" Us in Glendale, California, Pitt, 51, showed off the ink on his right arm of a cross with the letter A on one side and the initials of his kids, MPZSVK, on the other.
Although the tattoo is not new, this is the first time Pitt has been spotted sporting the ink.
The family spent an hour at the toy store picking out fun items for the kids. "They bought a whole bunch of Legos, slinkies and arts and crafts stuff," a source tells PEOPLE.
The source adds that Jolie and Pitt "were excited about the toys their kids were looking at and had questions about them."
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Pitt and Jolie are no strangers to tattoos with a special family meaning. The actress has one featuring the map coordinates of the birthplaces of Pitt and all of her children.
Reporting by NICOLE SANDS