If you are talking about like the 'nightmare child' and 'meanwhiles and neverweres led by the Could've been king'' that the Doctor would sometimes mention when talking about the horrors of the time war, they weren't alternate alien races taking part in the time war. They were weapons/events/experiments/things that got created by the Daleks and Timelords during the time war. When Matt Smith's doctor reboots the universe after the Pandorica, he says the remaining daleks are 'footprints of the never-were', which suggests some kind of parallel universe paradox crossing over into the time war. I mean, when both enemies can keep traveling back and forth in time, paradoxes get layered on top of paradoxes. Imagine if the daleks used time travel to setup an experiment group, sort of like that cult of skaro group, millions of years before the war, they evolve differently and more powerfully then normal daleks, with the sole intention of weaponizing themselves against time lords, and then you bring them back into the war when they are ready. That's basically what the 'Skaro Degradations' were, mutated daleks with some weird abilities. That one actually got described, but most of the others are left vague on purpose.Times like this always make me hopeful that this big baddie that's coming will be one of those vaguely mentioned things from past Who, like some of the things they fought against in the Time War. I'm sure it'll just end up being some new alien race, however.
Who you referring to?sigh... Why would he do that?
It wasn't, he was found as a baby. Unless that was the lie he told himself. In that case he could have just aged, I think you see a young John Hurt in a mirror when McGann regenerated.If yana was the form he took during the time war.. why wouldnt the doctor regonize him in utopia?