Complex sentence: The Senator of planet Alderaan and current owner of C-3PO and R2-D2, who is secretly one of the main leaders organizing the network of rebel cells that will eventually become the Rebel Alliance.
Split into simpler sentences: The Senator of planet Alderaan and current owner of C-3PO and R2-D2. Secretly, Organa is one of the main leaders organizing the network of rebel cells that will eventually become the Rebel Alliance.