The impression I got is that Thongvor, as head of the family, just put his brother there as a smokescreen. No-one can forfeit him, now, can they? Not if it was his brother's doing...

Also his name has 'thong' in it. Cannot unsee.

Awwww why would you say that? I'm going to be sick now.

Apparently, http://uesp.net/wiki/Online:A_Life_Barbaric_and_Brutal

I wouldn't be surprised if they continue to do so in the 4th Era.

That makes sense. Thonar calls himself the hands of the family. That means Thongvor gets to keep his reasonably clean.

If it makes you feel better, try to focus on http://www.uesp.net/wiki/Morrowind:Thong_of_Zainab.

There's also proof in that link up above that they are definite Daedra-worshippers.