The Septim Emperors are Dragonborn?

[Grove-of-Hares]

I can see it now...

Martin: "Do you need a priest? I don't think I'll be much heFUS RO DAH!!!"

[Porphyry]

Okay, if being Dragonborn means that all of one's children will be Dragonborn, that would mean that:
- At least one of the player's parents is Dragonborn
- The Player is of the Septim bloodline, which seems unlikely (it's not exactly prolific...)
- Being Dragonborn would be remarkably less rare, important and impressive

[Pilaf The Defiler]

Okay, if being Dragonborn means that all of one's children will be Dragonborn, that would mean that:

It doesn't, really. Read Book of the Dragonborn. That point is up for debate.

- At least one of the player's parents is Dragonborn

Not necessarily at all.

- The Player is of the Septim bloodline, which seems unlikely (it's not exactly prolific...)

There were many Dragonborn long before Septim. You meet one in Sovngarde.

- Being Dragonborn would be remarkably less rare, important and impressive

It's always been rare, but not unheard of.

[Porphyry]

Okay, if being Dragonborn means that all of one's children will be Dragonborn, that would mean that:

It doesn't, really. Read Book of the Dragonborn. That point is up for debate.

- At least one of the player's parents is Dragonborn

Not necessarily at all.

- The Player is of the Septim bloodline, which seems unlikely (it's not exactly prolific...)

There were many Dragonborn long before Septim. You meet one in Sovngarde.

- Being Dragonborn would be remarkably less rare, important and impressive

It's always been rare, but not unheard of.

Yes, thank you, I was well aware of that the OP was incorrect. Was attempting to further demonstrate that, actually.
Was aware that Tiber Septim was not the first Dragonborn, but didn't know about the whole going to Sovngarde bit. Haven't gotten that far in the main quest yet. Sounds like fun!
Again, thanks for explaining all that, I must have conveyed my point rather poorly.