Apart from the political confrontation, one of the reasons noteworthy for the 'exclusion of Prince Nagaya' was that the three princes, including Kashiwade no Okimi, who were given birth by Imperial Princess Kibi, an aunt of the emperor, (and of course the sons of Prince Nagaya) would have been the most promising successors to the Imperial Throne if something happened to the emperor and Prince Asaka.
政治的な対立もさることながら、天皇と安積親王に何かがあった場合には天皇の叔母・吉備内親王の生んだ男子（当然、長屋王の息子でもある）である膳夫王ら三王が男系皇族での皇位継承の最有力者となる筈であったことも「長屋王排除」の理由として注目すべき点である。