The thesis presented in Lecture Room E at the Faculty of Aerospace Engineering in Delft delves into the realm of sustainable aviation solutions, particularly focusing on the utilization of Liquid Hydrogen (LH2) in aircraft design. Highlighting LH2 as a promising option for sustainable aviation, the research emphasizes the use of rear-fuselage tanks for fuel integration in conventional tube and wing designs. While previous studies have acknowledged limitations related to the larger horizontal tailplane required for LH2 aircraft, this thesis introduces a novel industry approach of sharing a single tailplane among aircraft within an LH2-powered family. By exploring the concept of tailplane commonality, the study provides initial guidelines for designing LH2 aircraft families with rear tanks, with a specific emphasis on assessing performance penalties and comparing them to conventional kerosene-powered designs. A unique methodology has been developed to size the tailplane of LH2 aircraft during the preliminary design phase, considering potential family members and aiming to minimize performance impacts. The results of the research indicate that LH2 aircraft families may experience lower performance penalties due to tailplane commonality when compared to traditional kerosene-powered designs. Overall, the study sheds light on the efficiency and advantages of tailplane commonality in LH2 aircraft families, offering insights that can further propel the development of sustainable aviation solutions.