This is something that crossed my mind... Is it possible that the family heads could be using their own blood in their family members to make stronger kids? I am not talking about them merely having kids though. I am talking about a similar process to making princesses. Of course, the result wouldn't necessarily be the same as with princesses. Princesses get bullshit strong bodies from zahard's blood because that is a trait zahard has, a bullshit strong body. And that bullshit strong body is given to people on top of whatever other attribute they already have. So you have a koon or an eurasia with the physical might one could expect to inherit from zahard himself.... Anyways, the family heads would have little motivation to just give their blood to random people like zahard would as they already have families of their own but taking their own children and further strengthening them with their blood seems like something they have little reason to not do, unless the process does not work on people you are related with.