Original Fourth Doctor

An incarnation of the Doctor was seen during the Fourth Doctor's mindbending contest with Morbius. (TV: The Brain of Morbius, AUDIO: Cold Fusion) According to one account this man was an incarnation of the Other, whom the First Doctor was a reincarnation. (PROSE: Lungbarrow)

In this incarnation, the Doctor likely became a parent (if he wasn't already) with Patience as his first born was soon to be a father soon after he regenerated. After this the Doctor and Patience also had twelve other children. (PROSE: Cold Fusion, TV: An Unearthly Child et al.)

In her memories, Patience once remembered that this incarnation recently regenerated into another. His next incarnation was much taller and hairier than this one. (PROSE: Cold Fusion)

Behind the scenes
The face of this Doctor were first introduced in TV: The Brain of Morbius but it was not until AUDIO: Cold Fusion thirty years later, in 2016 thatthey were confirmed to be incarnations of the Doctor.

On the DVD of An Evening with Philip Hinchcliffe, Hinchcliffe said it didn't matter what fans say these mind battle faces are, he still considered himself an incarnation of the Doctor. He made this statement before it was revealed that the Morbius Doctors are incarnations of the Doctor and not Morbius.