(Susan points to the scanner where the picture has changed to that of a swampland accompanied by the cries of strange creatures.)The Tenth Doctor's offhand remark to Rose this evening that he was once a father, and my current binge of watching early First Doctor stories, plus my past irritation with Lungbarrow, have been making me put some effort into constructing my own prehistory of the Doctor.
Susan : Oh, I recognise that. That's where we nearly lost the TARDIS, four or five journeys back.
Doctor: Yes, the planet Quinnis.
The Tenth Doctor describes himself as having been a father; the First Doctor is introduced to us as a grandfather. This to me clearly means that his race have the potential for a parent-child relationship of the kind excluded by the Lungbarrow scenario.
(And while of course accepting that this is not necessarily a biological relationship, there are no grounds whatever for insisting that this must apply to the Doctor.)
It's also observable that when the Third Doctor was in an earth hospital in Spearhead from Space, while the human doctors exclaimed at his second heart, they didn't remark on any other aspects of his plumbing. It's also observable that female Gallifreyans have visible secondary sexual characteristics. (Speaking of secondary sexual charcteristics, are there any bearded Time Lords?) I therefore feel certain that Gallifreyans reproduce sexually, and not very differently from us humans.
(But I don't take the Leela/Andred relationship as useful evidence of interfertility between Gallifreyans and humans. While I accept that Leela is probably descended from earth humans, I don't think she did much research on Andred's biology. Though she may well have done some.)
So there's a whole history of two Gallifreyan generations in the Doctor's life before his arrival on Earth in 1963. I see there is various secondary canon literature on this, and I may well start reading it. Or, perhaps, more than just reading it.
Oh yeah, and it's noticeable that Ian doesn't spot anything odd about the Doctor's heartbeat in The Edge of Destruction. Maybe Gallifreyans get the second heart only when they first regenerate?