What information is on them?

check out http://www.uesp.net

It is a VERY usefull tool... It has a map of the tomb, and info on the Anrethi's.

Not much info. Just that there is a tomb and some people have the last name. I assume it is a Telvanni house name but that's about all I can get out of it.

The who?

NOOOOOOOOO idea...

Did a search at TIL; most important info was about the tomb and Vampires...

I see.

OP, do not delve into Morrowind's names, for that way lies madness.

A Gnar Mok peasant named Rotheran? Aryons everywhere, even in House Hlaalu? A Telvani (not Telvanni) in Sadrith Mora? Eek!

Let's not forget the Drens of Hlaalu which is just one letter away from the name of House Dres.

It's times like that you can tell the Devs were none to caring about people's names and just stuck them on NPC's without so much as a backward glance..

Not necessarily.

You act as if people don't walk around with the same last name or with names of establishments; I've known at least 2 people with the name McDonald.

Go count the number of Patricks in Melbourne.

Edit: Goddamnit! Disciple! You're on latrine duty!

Well, personally I already know of about 4...But what I was trying to say, and it's easier to spot in Morrowind with family tombs and then random NPC's but also there are some cases in Oblivion where it seems like the Devs have just taken an object or name, switched a couple of letters around and slap them on an NPC, sometimes they don't sound very lore correct either...