Re: 7X13 The Name Of The Doctor(Grading/Discussion)(SPOILERS!)
The Other is a legendary figure in Time Lord History. During era of the 7th Doctor, the script editor Andrew Cartmel felt that all the mystery of the character had gone and sought to reintroduce some mystery. The Cartmel Masterplan, it was dubbed later on by fanon.
There were several hints to to the fact that there was more to the Doctor then just another Time Lord, including a wonderful line "Remembrance of the Daleks" where the 7th Doctor is talking about the Hand of Omega, and mentions "And didn't we have problems with the prototype."
Basically the Other was part of a Triumvirate consisting of him, Rassilon & Omega.
For what it's worth, The Name of the Doctor pretty much rules out anything involving The Other - though not, I suppose, a similar idea - as it shows the Doctor and Susan stealing the TARDIS together, whereas Lungbarrow shows the Doctor stealing the TARDIS, travelling back into Gallifrey's past, and then rescuing the Other's granddaughter Susan, who then recognises the Doctor as being a new form of her grandfather.
"Some days are better than others. They say that where I come from."
"Loudly, I imagine, on the day you left."
(Blake's 7 - Rumours of Death)