As far as any references to peoples in Oblivion, I've got this:

Sinderion's remains
Lucien Lachance's spectral
Romlyn Dreth (descendent of Valen Dreth)
M'aiq (related to all the previous M'aiq's)
Amaund Motierre (related to Francois Motierre)
Movarth
Sheo

His doors are closed, but not locked.

*These are all Spoilers, of course*

Crassius Curio has written a dedication inside the Lusty Argonian Maid Folio added with Dragonborn.

There's a memorial stone in Windhelm for someone called Hrisskar who could possibly be the Nord Hrisskar from Seyda Neen.

Silus Vesuius is a descendant of someone from the Mythic Dawn.

All very tenuous, I know.

More solid ones are Captain Carius from Bloodmoon, the 3 Glenmoril witches, Isobel, Ettiene, and, um, the other one. And for someone who's very much alive there's Master Neloth.

Movarth Piquine is a cool one (I love stuff that references the in game books). And for books, anyone notice how Barenziah had that now censored love scene at the inn in Riften, and the inn in Riften is called The Bee and Barb?

I also Love St. Jiub.

Ah, but the Falmer loot and scavange just as we do....

Oh damn that flew right over my dirty little head till now XD

What about Savos Aren? Fathis Aren from Oblivion could be his grandfather, or at least related. They're both Mages who're a part of their Province's respective Mage Guild (Savos is in the College, Fathis is in the Cyrodiil Mages' Guild)

I'm also pretty sure they BOTH have a glitch related to sleeping; Savos can't find his bed because it's 1300 units away, while he's only allowed to search 500 units to find it; so he wanders around all night.
Fathis doesn't sleep because of a loading order issue.

I could be drawing invisible lines, but it just feels like they might be connected.

BTW; they're both Dunmer. Figured I should elaborate for those of you who don't know them.

EDIT: Apparently Dovyn Aren, a Dunmer Nightblade in the Thieves' Guild, has the same name too. He's in Oblivion.
Related? Mayhaps.

There's the remains of one of the last knights of the nine in the northern part of skyrim unfortunately.

Im surprised no-one has mentioned Karliah yet.

She is a descendant of Jagar Tharn and Barenziah.

What?

Photo? Proof? Must see.

Source?

http://www.uesp.net/wiki/Skyrim:The_Nightingales_Vol._2

The Nightingales Volume 2 is written by Gallus, and talks about Karliah's history. She is however not related to Jagar Tharn, but instead Drayven Indoril, a Nightingale hired by Jagar Tharn to seduce Barenziah.

"It is interesting to note that history refers to Jagar Tharn as "Nightingale" well after the point Drayven would have vanished from the story. The distortion of actual events is very typical of Barenziah's manipulation. With the pressure of blame falling squarely on her shoulders for Uriel Septim VII's imprisonment, she twisted the truth and created the notion that the "bard" named Nightingale was Jagar Tharn himself. She felt the tale of being enthralled by the master sorcerer held more of a forgiving if not romantic notion than simply being seduced by a master rogue. Some also further speculate that eliminating Drayven from history was her attempt at protecting the reputation of Jagar Tharn, whom she was rumored to have been quite fond of."

This is the author trying to make sense of history using facts available to him that are not as reliable as the facts known to us, the players, who were there for these events.

It doesnt really make sense for Barenziah to try and protect the name of Jagar Tharn, the man she spent all of Arena plotting to expose and depose.

The father of Karliah is Jagar Tharn, in disguise. http://www.uesp.net/wiki/Lore:The_Real_Barenziah_%28Daggerfall%29#Part_IX describes this quite well.

Karliah is a wonderful example of a character that is a throwback to some of the more influential and powerful people of the third era.

To the people wondering why Sinderion is stuck full of Dwemer arrows, I always thought that he had triggered a trap of some sort and stumbled back to his camp before expiring. :'(

IIRC, Neloth, Sheog, and Dervenin are the only characters to be met in person in both Skyrim and a previous game. Ocato is also confirmed to have been murdered in one of the ingame book, and it's implied that most of the Blades you met in Oblivion were killed by the Thalmor as well.

Well, I'd assumed that Gallus had gotten his accounting from Dralsi who was a nightingale before Karliah, and Gallus says Dralsi is Karliah's mother, not Barenziah and Jagar Tharn (or Nightingale) who were said to be Karliah's grandparents. Perhaps then my error is in the assumption. I admit I haven't read all the books in sometime.

http://www.youtube.com/watch?v=HWm7dcw9k6E

Don't forget the Carvains, who wander around until I rob them. They're related to the Count of Bruma.

Also, there's Medresi Dran and the Wandering Dead. Got to be a descendant/relative of Dovesi from whodunit?

How does that prove that, that corpse was a member of the Knights of the nine? He/she could have been any average person who died there while carrying a copy of that book. Doesn't mean that, that person was a member of the Knights of the nine.....

Carrying a knight standard, and copy of the book about the order. Probably not a knight.

Not trying to be a dike here or anything But a book or two next to a corpse doesn't really prove anything, had the flag next to the corpse have had the same colours as the Knights or an image like http://www.imperial-library.info/content/story-knights-nine I would be inclined to believe you but you can't simply base it on the fact that a corpse has a couple books pertaining to them as solid evidence that, that corpse was in fact a Knight.

The standard is rather tattered and worn and not recognizable, but I suppose he could just be some random hokerr of a knight who likes to carry around info of another order he's not a part of.

i dont think this would count but the essence of Lucien Lachance ?

I do

Right now in fact my Paladin build is carrying around a book on the Nightingales, so if I was to die on the battle field one might think that I was a member of the Nightingales It's not too uncommon for people to travel with a little reading material

Imho, I think Sinderion's death could only be attributed to the Dwarven Sphere outside. I'd assume it poked him full of holes, and he stumbled back inside. Stumbled, fell, and died either from knocking his head or blood loss.
Either that, or the Sphere went inside his little hideout and killed him while his guard was down. Either way, I think it was the Sphere. Considering it was Dwemer Arrows (bolts) and Falmer don't use those. Nothing except Dwemer traps and mechanisms use those.

So, it can be safely assumed (imo) that the Sphere killed him. I have no idea how long he managed to survive before the Sphere got a hold of him, but I doubt it was long. I'm surprised Sinderion even made it long enough to set up a home down there; we got attack instantly. It's possible he set off the Sphere somehow, considering it was already "awake" and guarding the door.
Likely, he was hurt by it (more like [censored] up completely) and went inside, locking the door behind him.

Then he died.