The pure human body born from love has regenerative and self-healing ability (divine spark/born from love/descendant of King). When a genetic experiment is performed and such a human does not die,the body produces its own antibodies as a defense for survival. But everything leaves a mark and it's basically a mutant.
But the next offspring of this "mutant" (born of love with a divine spark) will become very strong while having the abilities of its (genetically modified parents) has already innate.

Now imagine that it was "the set wording of the agreement" that the same species must not kill each other, but the parents of such an individual would be mutants of different "beings", going against each other.

Neither species could kill such a child, but the child would no longer be bound by this "agreement". So it would not only be able to reproduce more resistant offspring, but gradually the entire bloodline would be cleared through the maternal line.
2/3 mother, 1/3 father.