@Kriss10
Well he is human at first, he bacame a wolf later so maybe it's possible ...
And the story isn't in the modern age so, maybe they just don't know and try to have a heir no mater what.
@Mangareader
I'm pretty sure the prisoners were to test what remains of his humanity and to see if it was even possible for a human to survive in his presence. The prisoners were not put in to produce an heir with him.