
Spoiler
The doctor saves the ML brothers son (who is the FL new son) and so due to that he lives however before all this, the doctor was in charge of "creating" suitable brides for the bloodline and keeping them pure in order to continue the family purity.
The males of the family are born from a true pairing of sibilings. The females are born when a "pure" virgin and a male of the familiy ...do baby things.

Spoiler from what I remember
In addition to the fact that Damien is the MLS brother son, the ml brother doesn't even know that the person he got pregnant was his actual sister. Like bruh, so this doctor said that ml brother and the girl he fuvked with in giving birth to Damien was in reality "tru love"

SPOILER
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Basically all taran males are born oit of incest. They groom a girl since young, giving her herbs since their first period(the same herb that Lucia took to stop getting periods) and after they're grown up, the girl is given to cure so they can get period. After that a male member of the taran mates with the said girl and they're killed off after the baby is born( always a girl baby is born following this method). The female Taran members are used then to produce the heir by sleeping with their half brothers.
So, in essential all taran males are born out of incest and they in turn are expected to sleep with their half-sister to produce an heir. Some do it knowingly and some unknowingly. Likw in the case of Hugo( Hugh's twin) , he fell in love with his half-sister and wanted fo get married to her ( he didn't actually know that the girl is sister and neither did the girl)
wait someone remind me on what the doctor did