Antagonist.

Gilbert or "G", is the partner of Curtis, working alongside Curtis in order to bring Meryl back to Dr. Zacharias. G however, is far more relaxed and easy going. That doesn't just pertain to this mission, but in life in general. He doesn't take much all that seriously, and cracks jokes constantly. However, his lackluster attitude should not be seen as something to be underestimated, because just like Curtis, he too is skilled in self defense and has plenty of weapons training. He's not afraid to kill or carry out his missions, but he tends to talk through most of it.

He'd probably sound something like Quinton Flynn's Reno from Final Fantasy VII: Advent Children.