For what i find most probable:

If said bloodlines are real they are most probably related to old nephilim blood.

There is most certainly a top family directing others.

The jews took up worship of said leaders after the fall of their elohim god (or even before).

So no, the top is nephilim themselves imo, or atleast traceable descendants with much more neph blood than others. From which cannibalism etc as the 'gods' loved human sacrifice. One could posit if the genetic engineering wasn't also to have some better biocompatible food with their own biology.

In a sense even more than blackmail for the psycho peasants it is a reclaim of their own 'secret' identity and lineage.

But by now i wouldn't be surprised there is a big orgy of different powers rotating around that top, aliens and whatnot.