法苑珠林 8.96

8.96

爾時王子既安住已。憶父王語。於自姓中求覓婚姻。不能得婦。各納姨母及其姊妹。共為夫妻依於婦禮。一隨王教。二恐釋種雜亂相生。

At that time, after the princes had settled, they remembered their father the king's words to seek marriage within their own clan. Unable to find wives, they each took maternal aunts and their own sisters to be husband and wife according to marital rites: first, in compliance with the king's instruction; second, for fear that the Śākya clan would become intermingled and mixed in their procreation.