Unfortunately, seeing that she had her granddaddy's color palette + knowing Setina wanna protect that love and family, according to granddaddy, she is a biological daughter. She just inherited that recessive gene and because this is not set in modern times, people still don't know that we can actually inherit things from our grandparents and even from our distant ancestors, not just to our parents, making genetics a weird shit.
The dad's just an asshole who wanna lash out his anger towards the daughter who doesn't resemble him or his wife and what justified his anger was the fact that since their house boast aura and Iris didn't have an aura, it's natural for him to treat such 'useless' daughter that way.
F*ck the noses... Tell me why does the dad hates Iris? She's also biological daughter tho ain't she?