I'm not sure where I came across this -- but checking in this thread for at least two months back doesn't reveal it, so I feel safe putting a rec here. (Which I am, btw, mostly plagiarizing from the rec I put up on TV Tropes a few days ago.)
Yes, I am Harry's Brother. A few years after the events of Halloween 1981, the wraith of Voldemort finds 4 Privet Drive and Harry Potter -- and is accidentally incarnated into a near-clone of Harry's 6-year-old body when the soul fragment in the child's scar spontaneously rejoins with the Dark Lord's spirit. Using every bit of his cunning and experience, the re-youthened Voldemort then escapes and begins a long process that results in him returning to Privet Drive at age eight in the guise of Harry's half-brother, the result of an affair James Potter had with an American woman — with the goal of studying Harry to learn what the prophesied "Power he knows not" might be. Along the way, Voldemort kills many, many people — and gives Harry a much happier life. Then comes Hogwarts...
A very interesting story told entirely from Voldemort's point of view. Voldemort is a Complete Monster, of course, except we learn that there's far more to him than just the homicidal maniac that the canon Harry sees once a year, and maybe -- just maybe -- he's Becoming The Mask from playing Harry's half-brother even as the death toll among canon characters at his hands keeps escalating. The author is very subtle about it though -- "Vito Potter" sometimes feels like he's just a few weeks from a Heel Face Turn, and then he'll turn around and a professor will be dead for getting too close to his secret; the reader is never sure which part of his personality is the "real" one. He seems strangely protective of Harry and even some of their friends, while at the same time plotting their eventual destruction when he comes back into power.
-- Bob
---------
Then the horns kicked in...
...and my shoes began to squeak.
Yes, I am Harry's Brother. A few years after the events of Halloween 1981, the wraith of Voldemort finds 4 Privet Drive and Harry Potter -- and is accidentally incarnated into a near-clone of Harry's 6-year-old body when the soul fragment in the child's scar spontaneously rejoins with the Dark Lord's spirit. Using every bit of his cunning and experience, the re-youthened Voldemort then escapes and begins a long process that results in him returning to Privet Drive at age eight in the guise of Harry's half-brother, the result of an affair James Potter had with an American woman — with the goal of studying Harry to learn what the prophesied "Power he knows not" might be. Along the way, Voldemort kills many, many people — and gives Harry a much happier life. Then comes Hogwarts...
A very interesting story told entirely from Voldemort's point of view. Voldemort is a Complete Monster, of course, except we learn that there's far more to him than just the homicidal maniac that the canon Harry sees once a year, and maybe -- just maybe -- he's Becoming The Mask from playing Harry's half-brother even as the death toll among canon characters at his hands keeps escalating. The author is very subtle about it though -- "Vito Potter" sometimes feels like he's just a few weeks from a Heel Face Turn, and then he'll turn around and a professor will be dead for getting too close to his secret; the reader is never sure which part of his personality is the "real" one. He seems strangely protective of Harry and even some of their friends, while at the same time plotting their eventual destruction when he comes back into power.
-- Bob
---------
Then the horns kicked in...
...and my shoes began to squeak.