Gemini Twins by Johnathan Brazee

Done with school and getting ready for the future as adults . . . until alien slavers attack! Identical twins Nika and Rika Ingersoll watch from hiding as their mother and others are captured and are bound and determined to save them before they are taken off-planet. If the aliens leave with their human slaves before the Navy and Marines can arrive and attempt a rescue, those captured will never be seen again.