Recall the Earth — Kyle Pratt

Lucas's sister, Katherine, smuggles Rachel to their home planet in the Devon system, but when they arrive, Prince Draven and the soldiers of Nightwatch wait to kill them. Seriously wounded in battle on another world, Lucas has no idea of the danger facing his sister and Rachel, or that the Valac are fighting to surround his home world. His entire family may die before he can do anything to save them. But stories of Rachel and Earth are spreading, even as Nightwatch strives to arrest or kill all those who learn the truth. Recall the Earth is the second book in the Guardian Knights of Terra series.