Alexander was a former lover of Lwaxana Troi.

In 2368, when Lwaxana's daughter Deanna Troi introduced Alexander Rozhenko to her mother, Lwaxana expressed how wonderful a name Alexander was. She once knew an Alexander, whom she described as a tall, handsome warrior, that adored her and followed her everywhere. (TNG: "Cost of Living")

This character was only mentioned in dialogue.