Motohiro MIBU was the second son of Princess Shigeko, the first daughter of the Emperor Showa, and Morihiro HIGASHIKUNINOMIYA was the first son of Naruhikoo HIGASHIKUNINOMIYA.
壬生基博（もとひろ）は、昭和天皇の第1皇女成子内親王と東久邇宮稔彦王の長男東久邇盛厚（もりひろ）の二男。