User blog comment:B214/Volume 23 discussion blog/@comment-77.188.250.151-20170426032010/@comment-29963364-20170426071905

Or perhaps it was another "glitch" in the [Sacred Gear System].

God never foresaw humans being reincarnated into Devils, so perhaps, since Rudiger was originally human, the System registered his child as "human." But since the child is a Devil born from a Reincarnated Devil, the System "glitched", causing negative effects for the child.

I know that it was established that some people are born with SG's that negatively effect them (even kill them), and Rudiger's son was one of those people, but maybe the "glitch" also contributed to that.