Why can't Wrath as a King fight alongside his brothers?

Wrath cannot fight because with him being king and the only pure blooded vampire left if he died their would be no true vampire left in the race and the race would die out because their would be no-one to rule them, because he doesnt have a son/daughter who could take over the role as king/queen lol soz its a bit long xxx

Well, Beth is the queen so she can rule if Wrath die... Right?