《资治通鉴·魏纪·魏纪六》
由此说来，并不是皇族子弟偏偏在惠帝、文帝之际忠孝双全，而在哀帝、平帝之际就变成叛逆，是权力轻微，势力薄弱，不能平定祸乱而已。
由斯言之，非宗子独忠孝于惠、文之间而叛逆于哀、平之际也，徒权轻势弱，不能有定耳。
From this we can see that it's not that the children of the imperial family were especially loyal and filial during the reigns of Emperor Hui and Emperor Wen, and then became rebellious during the reigns of Emperor Ai and Emperor Ping, but that their power was weak and their forces insignificant, and they were unable to quell the chaos.