The thing that bothers a lot of people is that WRATHGAR may have killed his family, but he won’t deny that he hasn’t. I don’t believe he’s capable of this sort of thing, but all he has to do is dig up the corpses and show us where he did not cave in their skulls with a hammer, and he’s not done it.
Sure, he might say that they’re alive and well, but how can we trust someone who won’t prove that he did not kill his family? If they are alive, and having never seen them, I can’t say that they are, how do we know they aren’t doppelganger sex slaves? There’s really no way of truly knowing without the corpses. What WRATHGAR needs to do is show us the mummy.