Luke Koonan is Chaz Koonan and Vanessa Koonan's second son. He is the younger brother of Matthew Koonan.

Along with their mother, Matthew and Luke were transferred to Sol, as the Pandoran fleet closed in on the system. The two boys came to the White Knights' final meal together, the first time that any of the team (aside from Chaz) had seen them and Vanessa.

While Matthew was excited to see his father, Luke was initially intimidated by Chaz and refused to leave Vanessa's side. After some encouragement from his mother and Matthew, however, he accepted Chaz for who he was and hugged him.