Enlighthen me, is Nol their biological son, illegitimate or adopted ?

I think he's the dad's for sure.....definitely not the snake's child though. Plus they keep referencing "she" "mother" "her" as well as a 5 yrs ago so my assumption is, his real mom died about 5 years ago but he was removed from her side when he was younger. The snake then had to "raise" him but she appears to be violent judging by the way he fliches away from her. So maybe illegitimate or snake and dad divorced for a while and bam nol came out. Plus he's the only one with a Korean name from the fam which is also sus