K'Kath was a hologram of an adolescent Klingon who was friends with Jeffrey and Larg.

K'Kath was added to The Doctor's holographic family program by B'Elanna Torres in an effort to make the picture-perfect family more realistic. He subsequently forbade his son to see either Larg or K'Kath and suggested that Jeffrey should find some nice Vulcan friends. However, the ban was lifted by Charlene, who questioned The Doctor's new family rules and schedules.

In this modified version, K'Kath, along with Larg, supplied Jeffrey with a kut'luch with which the Human boy was supposed to kill an innocent person in order to prepare himself for his future life as a warrior. The Doctor did not approve of this ritual, and told the two Klingons to leave. (VOY: "Real Life")

K'Kath was played by Chad Haywood.