It has to do with how any race can be Dragonborn, and how Tiber Septim's race doesn't really matter in terms of the line of emperors he started.

No, it's not hereditary. It is a blessing from Akatosh.

The Dragonborn is a Thalmor Altmer

Ummm did you read the book?

It doesn’t provide definitive answers to anything…
Just cause not all dragonborn are related does not mean it is not hereditary. It is a mystery (as the writer points out) but the writer was not privy to the knowledge that we have, Martin was Dragonborn without ever lighting the fires, Reman was Dragonborn without lighting the fires either which means they had to be born that way. It is still not definitive but there are more reasons to accept a hereditary conection rather than reject it.

Did you? It does not say black on white that it can't be hereditary, but it says it doesn't have to be. In other words: The Septims does not have anything to do with our character. Neither does our charcters family.

That makes the most sense of anything I've heard so far, but if it isn't genetic, then why was the entire septim line Dragonborn? If anyone can be Dragonborn, I don't see why it happened to an entire family, and then one guy 200 years later. Maybe I'm just thinking too hard about this.

Maybe the bloodline didnt have actually anything to do with it other than for Akatosh to have an easy time of naming new Dragonborns

Now before I start, I know in the game the Dragonborn can be any race, but I'm talking about in lore, not your game.

1) In Skyrim, It seems like it makes the most sense for the Dragonborn to be a Nord, since the game takes place in the home of the Nords, and the whole thing sort of revolves around Nordic beliefs and prophecies. Plus the Dragonborn was portrayed as a Nord in all the pre-release stuff.

2) But the Septims were all Dragonborn, their dragon blood was what gave the Septim line their power to be emperors. Anyone who has played Oblivion a lot should know this. And Tiber Septim was the first of these Dragonborn emperors, so I'd always assumed he was an Imperial, just like the rest of the Septims. That would make sense right?

3) But in Skyrim it seems like the Nords believe Tiber Septim was a Nord... which would make sense in relation to my first part about the Dragonborn being a Nord. But if Tiber Septim was a Nord, how did he produce a line of Imperials? So are the Nords wrong, and was Tiber Septim an Imperial, meaning it would make sense for the Dragonborn to be an Imperial?

I guess I'm just pretty confused about the whole thing... Does anyone else have thoughts on the matter?

Yes and Septim was not related to Reman, but all of their kids were Dragonborn all the same. The most likely conclusion is that the blessing is hereditary but not all who have it are related.

It might be hereditary, but seeing as the emperors were supposed to keep the covenant with Akatosh he may just have made the families Dragonborn to make it easier to uphold the barrier. What we know is that it does not need to be hereditary and that Akatosh probably can chose who becomes Dragonborn whenever he wants.

Tiber Septim was dragonborn long before he became emperor, so was Reman. Being an Emperor had nothing to do with it for them. Martin had a father who was dragonborn emperor but never became emperor himself yet he was dragonborn. Using your logic we can argue that all dunmer are born as Chimer but Azura is still pissed and she converts each and every single one of them to Dunmer. Thus no one is hereditarily Dunmer, they are just cursed by Azura.

Would the Septims be Dragonborn if Talos never recovered the Amulet of Kings so they could re-light the Dragonfires everytime a new emperor is crowned? We do not know. Is it known if the Cyrodiil family(the Reman Emperors) were all Dragonborn? No. Is it known if a decendant from Alessia would be Dragonborn? No. There simply aren't enough proof to conclude that it is hereditary, much like you cannot actually prove wheter the big bang happened or not.

Is there any proof that the blessing gets bestowed regularly? No there is non, zip, nada. No data whatsoever. Is there evidence that suggests that it is hereditary. YES plenty of it.

We know that their descendants were Dragon born because they were able to wear the Amulet of Kings. The amulet of kings is not attuned to the royal bloodline it is attuned to the dragonblood.

No, but there is proof that it is bestowed. Someone have to get it from Akatosh, even if it happens to be herditary. Before Bethesda clearify this I am not going to change my mind, because I do not see any proof that it is hereditary.

Pelagius was dragonborn, but he was insane and was more a worshiper of Sheogorath(probably unknowingly) than he was of Akatosh yet he still had the blessing bestowed upon him??? You would think Akotosh would skip that one, but no. You would think that the god of time would have enough time to think things through, guess not. Or we can stop bad mouthing the most powerful aedric deity and accept that its hereditary. Hmmm tough choice, I love bad mouthing deities.

snip