I'm in digital contact with the man who invented time travel, HK. From some knowledge he shared from different worldlines, certain facts are coming to light. Some of you may find this interesting, and if nothing else this can serve as a record in case I failed.
Two major facts stand out.
There is only one world
I have spoken of worldlines often, but they are not parallel worlds. They are alternative, possible states of affairs, with similar ones grouped together in an 'attractor field'. Think of it like a rope; it looks like one thing, but it's made of multiple strands, and multiple threads.
What matters is, none of these alternatives are real. There may be a multiverse (it seems likely) but that is independent of the worldline model.
Think of every entity in our world as a list: every property, and every event that happens to them is on that list. Altering the worldline is scratching out a term on that list, and writing another. This is important: it's not replacing a term, it's merely writing over it.
There are accounts of people recalling events from other worldlines. HK is one of them, and in a previous issue with time travel, he found many other situations. This would only be possible if the same people existed over multiple worldlines, rather than being multiple, different people who happen to share a history. We are the same people, no matter the worldline we are on.
The science isn't fully understood. It may be possible for non-conscious items to do something similar, but their physical properties would not change; this is conservation of energy, in a way. Their traits couldn't alter if it would change mass for just that object.
Memories however, as non-physical, massless objects are exempt. It is possible to reclaim memories from past worldlines. I am not certain of the mechanism: some people may have a natural inclination. It may be somehow contagious: the only situations I know of came from contact with someone who naturally possessed the ability (after a childhood illness: though that may just have been their first experience). If an illness causes it though, it may be triggered by some alteration to the physical brain.
From this, it follows:
It is impossible to never be born
Time may change, but as it is only the properties of memory, location etc that alter, at not the fundamental of the universe, energy must remain conserved.
The only seeming exception to this rule would be a time traveller, who travels from the future, and changes it. Would this make them never be born?
However, if they were never born, the mass and energy that makes that traveller up would not exist. Extra mass would have come, uncaused, into the universe.
In theory, this means that if a time traveller dies in the past, they would fail to change the future: the attractor field, without intervention, would draw the worldline back to one where they go to the past: so that they would be born, and travel back in time, so that their mass comes from somewhere. A mission could only suceed is they travel back to their time, in which case they would presumably be lost in the transition.
And then, later, when the time traveller is born, they would represent the mass that had existed in the past. Conservation of energy is not necessarily continuous, but everything must exist. Even if, in this new worldline, time travel is never invented, the energy remains conserved.
I hope this aids in understanding time travel, for any readers or other travellers.