法華義疏 12.108

12.108

觀音菩薩託生為子，故下現童男女身。又母子之業雖由宿緣，而不決定，今修福力，故令好人託生。

Bodhisattva Avalokiteśvara takes birth as their child; hence below he manifests the bodies of a boy and a girl. Furthermore, although the karma between mother and child stems from past conditions, it is not fixed; by now cultivating the power of merit, an excellent person is caused to take birth.