The Doctor's reality (An Unearthly Child)

In Auld Mortality's universe, the Doctor asked Susan to come with him as he made his escape from Gallifrey, and the Possibility Generator detected several branching timelines in which she agreed, (AUDIO: Auld Mortality) including one where the Doctor and Susan came to live in Barnes Common (PROSE: Doctor Who in an Exciting Adventure with the Daleks) and one where the Doctor and Susan came to live in Totter's Lane. (TV: An Unearthly Child) Both of these outcomes led to an encounter with the Daleks on Skaro. (TV: The Daleks)

However, other parallel possibilities involved Susan saying no, (AUDIO: Auld Mortality) and further accounts showed the Doctor living a parallel version of the First Doctor's life in which Susan declined and the Doctor subsequently never met Ian Chesterton and Barbara Wright. (AUDIO: A Storm of Angels, PROSE: The Innocents)

Relation to other realities

During the Last Great Time War, the Time Lords were aware of multiple, alternative accounts of the Doctor's first encounter with the Daleks, all of which involved Ian Chesterton. (AUDIO: Sphere of Influence, PROSE: Dalek Combat Training Manual)