“You flatter yourself, Doctor. In the end, you are merely another Time Lord.”
“Oh, Davros, I am far more than just another Time Lord.”
(s25s01: Remembrance of the Daleks)
In short? Yes.
There’s this thing called the Cartmel Masterplan which shows up in the 80s and 90s, introducing a figure of Gallifreyan history known only as “the Other”. The Other was one of the founders of Time Lord society, alongside Rassilon, Omega, Pandak, Apeiron, and Eutenoyar, and they were, for the most part, a mystery, lost to time, without a name, face, or background to put to the title.
The Other might not have even been Gallifreyan, and it does rather make sense for the alien founder to be called “the Other”, especially in a society like theirs. Rassilon and the Other didn’t really get along, er, at all. Rassilon had Omega killed and began a despotic rule over Gallifrey, sealing the borders, and the Other committed suicide, throwing themselves into the first Loom. Their accomplishments were, for the most part, either lost or covered up by Rassilon in his quest to cement himself as Gallifrey’s god.
A couple million years later, an Oldblood chronarch known to their peers as Theta Sigma ([coughs loudly])* was Loomed to the House of Lungbarrow. Their name day fell on Otherstide, the holiday celebrated in honour of the Other. And they were a bit… odd. They only had a single heart, and were likely something of an evolutionary throwback (although “evolution” isn’t perhaps the word here, as that implies alteration through chance, which the development of the Gallifreyans was certainly not), with telepathic centres much more like that of a Gallifreyan from the Dark Times.
They had conflicting memories and could speak Old High Gallifreyan, which was by their time a dead language. And through a series of rather murky events, they were forced to leave Gallifrey, taking with them their granddaughter Arkytior. They went to Earth, and Arkytior took the name “Susan Foreman” when she attended a secondary school in 1963 Shoreditch. Theta Sigma became known as “the Doctor”, and there our story begins.
* Theta Sigma (ΘΣ) is a short-form for the Greek name of the Judeo-Christian God, ΘΕΟΣ. The Greek word for “who” is “OΣ”. Andrew Cartmel, Ben Aaronovitch, and Marc Platt were very much aware of this.
“I know your secrets.”
“Very well, tell them.”
“I shall tell them of Gallifrey, tell them of the old time, the time of chaos.”
(s25s03: Silver Nemesis)
I’m still a bit confused. I knew that Theta Sigma is The Doctor, but as we all know, The Doctor has two hearts. Did he get the second one because of a regeneration?
Yes. In the spirit of not over-complicating things (I could talk about this for ages), the Doctor gained a second heart upon first regeneration, as Oldbloods are generally purported to do [The Man in the Velvet Mask, 1996]. The First Doctor had a single heart, as seen in s01s03: The Edge of Destruction.
For more information about Gallifreyan physiology, feel free to look at this powerpoint or send me an ask.