The Onasi family, a Human lineage, made their home on Telos IV during the period known as the Mandalorian Wars. Carth Onasi, the family's head, distinguished himself as one of the most accomplished pilots within the Navy of the Galactic Republic, ultimately achieving the high-ranking position of Admiral. He was married to Morgana Onasi, and they had a single child, a son named Dustil.
As the Jedi Civil War commenced, Telos IV suffered a devastating bombardment by the Sith fleet. Carth, who was serving away on military duty, returned to a horrific scene: his wife was mortally wounded, and his son had vanished. Unknown to Carth, Dustil had been abducted by the Sith. Presuming the worst, Carth eventually ceased his search.
Years passed before father and son were reunited, but the circumstances were far from ideal. Dustil had become a member of the Sith Academy located on Korriban. He held his father responsible for the tragedies that had befallen their family. Disheartened by his son's path, Carth pledged to rectify the situation.
With the assistance of Revan, Carth successfully persuaded his son to abandon the Sith. They made arrangements to meet once more on Telos IV.
Sometime later, an unspecific monument was erected in Coronet City on Corellia to honor a member of the Onasi family, although the exact reason remains unknown. By the time of the Galactic War, Mandalorian mercenaries hired by the Empire to aid in their invasion and subsequent occupation of Corellia had destroyed it.
Although the game files do not explicitly name Carth's deceased wife, David Gaider, the BioWare writer responsible for the character, identified her as "Morgana." This name was later officially recognized with the publication of the Knights of the Old Republic Handbook.
Dustil Onasi's enrollment as a Sith student at the Sith Academy on Korriban suggests that Force-sensitive abilities may have been present in the Onasi bloodline, possibly inherited from Carth (whose exceptional intuition and piloting skills hint at this), Morgana, or both.