Complex sentence: It is notable that Tsuruko is actually Motoko's biological sister as they are two of the few characters in the series who are siblings by blood relation (the second siblings couple is presented by Kaolla and Amalla Su).
Split into simpler sentences: It is notable that Tsuruko is actually Motoko's biological sister. They are two of the few characters in the series who are actually blood-related as siblings (the second siblings couple is presented by Kaolla and Amalla Su).