Cosmo first appeared in episode 53 of Sonic X. Her former home pagina world was destroyed door the Metarex before she was born, and she was instead raised on a space colony. She lived peacefully there until the Metarex came and began to destroy her new home, including her family (including her mother, Hertia). As Cosmo was escaping, the Metarex planted a tracking device on her. Cosmo also had a device inside her brain which, when activated, allowed the Metarex to hear and see everything that she did.

After the attack, Cosmo escaped into a ship and arrived on Sonic's planet. Miles "Tails" Prower, Cream,...

Family:
The only confirmed members of Cosmo's family is her mother Hertia (Earthia in the English dub), who is the leader of the Green Planet council, and her older sister, Galaxina, who worries about Cosmo and her mother.

Earthia/Hertia: Her mother, who is the leader of the Green Planet council. She decides to leave the planet when it becomes too dangerous, but is later killed after the Metarex board her refugee ship. In the dub version of Sonic X, she is instead known as Earthia. During Episode 78, she appears to Dark Oak--now returned to his form as Lucas--and speaks with him, telling him...