From The TimeSplitters Wiki

The main protagonist of the Timesplitters series is the burly, bald and bad Sergeant Cortez. He appears in the last two Timesplitters games, and is theoretically the main character of the first, though there is little evidence to prove or disprove this notion.

As head of an elite unit of space marines, Cortez was one of the leading combatants in the Timesplitter War, and the best soldier of The General. He fought bravely besides Corporal Hart and two Privates who were killed in battle before we came to know them. Rather than replacing them, Cortez chose to operate the unit with just two people, himself and Hart, feeling it best to work with those he trusted would get the job done.