And what's the big?
The nation's top cop - who is the first Hispanic attorney general - has become a point man for the White House on immigration reforms President Bush is pushing.
"Three of my grandparents were born in Mexico. They came to Texas," Gonzales told CNN.
Pressed by Wolf Blitzer, Gonzales conceded he didn't know if they came across the border like millions of illegal immigrants at issue in the current debate.
"It's unclear. It's unclear," Gonzales said. "And I've looked at this issue, I've talked to my parents about it, and it's just not clear."
Gonzales has often cited his grandparents' Mexican heritage and his dirt-poor upbringing in Texas in a big family headed by his migrant worker parents.
"My grandparents were Mexican immigrants. I remember visiting them as a very young boy - there was no telephone in their house, no television, no running hot water," Gonzales said during a naturalization ceremony for new citizens in December.
Gonzales is the latest in a series of Washington politicians to talk about their immigrant heritage.
Sen. Pete Domenici, R-N.M., recently recalled how his illegal Italian-immigrant mother was arrested by federal authorities in 1943.