Reittan Grax was a prominent Betazoid official. He was an old friend of Lwaxana Troi's first husband and had known her daughter, Deanna Troi, since childhood. He once told Lwaxana that he had a nice nephew that she thought would make a good husband for Deanna.
On stardate 30625.1, in 2328, Lwaxana wrote in her journal, "I'm so mad at Ian. I thought we were going to be alone, but he invited his buddy, Reittan and his girlfriend, along with us on our picnic. Not only does Reittan have dreadful taste in music, but his girlfriend has the most annoying laugh. I could barely tolerate her. Ian's going to get an earful." (TNG: "Dark Page", okudagram)
In late 2366, Grax was the director of the biennial Trade Agreements Conference held on Betazed. Despite being uncomfortable with species whose minds are unreadable by telepaths, Grax invited the Ferengi to this conference.
Grax attempted to contact the USS Enterprise-D for two days before finally being able to inform Captain Jean-Luc Picard that William T. Riker, Deanna Troi, and Lwaxana Troi were missing. He later assisted the Enterprise-D's crew in determining their whereabouts. (TNG: "Ménage à Troi")