In A.C. 188, Leia Barton worked as a nurse in a Barton Foundation hospital in the X-18999 colony, built by her father Dekim Barton for his workers. There, she met Treize Khushrenada, then an instructor for the newly founded Specials, who was wounded after taking a shot meant for cadet Lucrezia Noin.
In A.C. 189, Leia gave birth to a daughter, Mariemaia Barton. It is unknown who the father was, however, both Dekim and Mariemaia herself would claim that it was Treize. Mariemaia told Relena Darlian that DNA testing proved that Treize was her father. Unfortunately, Leia passed away only two years after from an illness.
Since Leia passed away when she was only two, Mariemaia had no memories of her mother. However, when she was still alive, she gifted Mariemaia a a red music box, which played a song called "Endless Waltz", as a Christmas present. Mariemaia treasured the music box greatly, and always had it on her person.