Kevin McNamara was a member of the Zion Cluster, an intergalactic organization devoted to the annihilation of war through any means necessary. If John Shepard was the brains of the Cluster, McNamara was most certainly the dagger. He was part of Shepard's personal elite, the Frumentarii. His roles were elimination, capture and super-covert recon.
When Tahar'ok was revived, McNamara tracked him down and brought him to his personal frigate, the Ptolemaios. McNamara was surprised that Tahar'ok came so easily, and guessed that it was just to get closer to John Shepard. Tahar'ok remarked that McNamara was "quite wise for a flesh-runt". Suddenly, their conversation was interrupted by Veronica Santangelo's nearby battle with Viriathus. McNamara pleaded with Tahar'ok to stay, but the Ta'har ignored him and left to save Veronica in the Epyon. When the Aries docked with the Ptolemaios, McNamara ordered the ship to go to warp. He soon arrived at Side 8.
His status after the destruction of Side 8 is unknown, but if he was still aboard it during the Battle of Side 8, he probably didn't survive.