If you saw what you thought was a Chevy Suburban but with a GMC grille on the front, then you were actually seeing the GMC Yukon XL. It's just the GMC version of the Suburban. But it's aimed at a different market segment than the Suburban is.
Chevrolet vehicles always have some sort of crossbar with the Chevy emblem on their front ends. GMC trucks never have a crossbar.
