Merlin--Always Saving Arthur's Arse

When Harry's twin is hit by Voldemort's killing curse, he becomes someone who had never been born. In the blink of an eye, he goes from his house in Godric's Hollow to a little cottage in Ealdor. It's centuries in the past and suddenly, people are calling him Merlin. And as it turns out, Harry is the once and future king reincarnated. What a mess of mixed up prophesies.