Lost planet series volume 1
Waking up on a distant planet, Chase Garrety is horrified to learn that he has no memory of his life and finds himself under the protection of a mysterious benefactor who requires him to complete an important mission before time runs out.
Lost planet series volume 2
"Chase has been reunited with his younger sister, Lilli. He doesn't remember his past, but Lilli does--she remembers their parents, and life before their planet was destroyed"--