Orphans of Space-Time

What happens if you travel back in time and change history so much it prevents your own birth?
You won't cease to exist; but when you return to your own time, nobody will remember you. Everything, as you remember it, will have changed. You still exist.
You’re a time orphan.
There are some who can remember people and events that stopped existing because a time traveller went back and changed it. That memory is a sign you are a time traveller - you just have to learn how
Orphans of Space-Time is a collection of short stories and novellas set in the Time Orphan universe

Drake was sure he had a childhood friend named Timmy. But evidently, Timmy never existed. Though he knew so much about him, nobody had heard of him. It just didn’t make any sense. Now, many years later, when Drake looks further, he finds himself on the trail of a dangerous time-travelling assassin.