Taint of the Blood

I was dreaming, but waking. There was something to do with someone being the son of an evil man and not being trusted by the fae because of it. My waking brain said that was not fair and why should it matter anyway? And then it came to me, blood calls to blood. It may not be nearly so powerful as having the blood of the person himself, but the blood of a parent could be used in a spell of influence, of mind control, over the son. So of course he is always in danger should the father ever have the skills he had a ready supply of what he needs to assert control over his son. Creapy stuff.