Even for Magical Creatures, inbreeding can cause problems.
However, since these issues could be regulated with Magic, they weren't a major concern. This was one of the essential forms of magic for breeding Demons, and Isaac, naturally, knew it as well.
But in reality, it wasn't just used for breeding Demons; it could be used on people too.
What's interesting, though, is that this magic wasn't originally developed for breeding Demons.
Many nobles with powerful bloodlines, seeking to prevent their lineage from being diluted, would often choose to marry within their clan. Over long periods of time, and given their extended lifespans, relationships between siblings became commonplace—to say nothing of pairings between mother and son, or father and daughter.
Consequently, the drawbacks of inbreeding appeared, and along with them, the magic to resolve these issues.
To this day, many nobles still use this method to maintain the purity of their bloodlines.
