Ah'rek Odé was a male Sith Pureblood who served as a Jedi Knight during the Great Galactic War, leaving the Jedi Order voluntarily at the age of 37- shortly after the Battle of Ilum in 12 ATC. Having developed romantic feelings for his Padawan, Harlem Minstyngar, Ah'rek decided the most appropriate course of action was a period of self-reflection outside the Jedi Order.
To everyone's surprise, Harlem left the Order less than a year later, tracking down Ah'rek as he travelled the edge of Republic space lending aid to those in need. Previously unaware of Ah'rek's feelings, Harlem revealed that he felt the same, and wished to be with him outside the Order, a proposition Ah'rek initially rejected until a few months later, at which point he accepted that his former student would not be dissuaded and did not intend to return to the Order despite his insistence.
As such, Ah'rek never returned either, and by the Invasion of Ossus Odé and Minstyngar were happily married.