Xon (David Gautreaux) never got to play this Vulcan character, now I wonder why? He was supposed to be the USS Enterprise NCC 1701 Science Officer in the never made Star Trek II, long story short Nimoy's I am not Spock soon switched when the idea of a multi million dollar movie was in the wind. The rest you can guess. Gautreaux got a small part in Star Trek The Motion
Yangs are the bitter enemies of the Kohms in the less than subtle allegory that was "the Omega Glory."
Live Long and Prosper.