Harry is a powerful baby. He is also a genius compared to his father and on an IQ test would have scored 220 to her 190. Remus and Peter were around a bit, always saying that Harry looked like a twin James with Lilies eyes. Sirius and the McKinnons, who delivered Harry always said that. It was when his mother, Lily, was freaking out and mumbling about how she wish there were two of her, so she could do everything to protect Harry, James, and herself. This lead to Harry slowly creating a twin from himself. Then once, when his mum fell asleep with him, he drew some out of her. He accidently let tiny Harry and Tiny Lily join into one. They got bigger, almost a quarter as big as him. So whenever Lily breast fed, or fell asleep with him he started making another her. Then added the smaller him. Soon, she was more than half was as big as he was.
The smaller Lily was getting hard to hide, she looked just like Lily, with a bit of Harry, as that part of him stayed. The McKinnons were killed, so only Harry, James, Sirius, and Lily knew there was no twin. The Lily clone loved Harry, she was learning magic and showing Harry how to do things with a 'wand'. The stick worked as they just had the magic come out the end. The more of Lily he put into little Lily, the more she understood.
Then that night came. Tom saw another baby in the room under the crib. That is why he laughed so horrible and killed Lily. He thought he could use the girl baby to further bind Peter and Severus. The problem was Harry was pulling Lily to the smaller Lily. He saw her love for him and pulled it into Lily and himself, to protect Little Lilly. Before then, Little Lilly was bound to Harry, as she had no soul. When Lily's soul was ejected by Tom's spell, Harry had bound it to Little Lily, not understanding she had died. The soul went into Little Lily, but the drawing magic was active when Tom cast his killing curse.
This led to both getting a scar, him on his right forehead and her on left shoulder. The killing curse went to Harry's forehead, split between them, reinforced the magic and blasted it out her shoulder into Tom. He was disintegrated. All his living flesh gone. Peter scurried in saw the robes, bag, and wand. He grabbed the bag and wand, heard Hagrid and changed, then fled. He made it out of the anti-transport ward, when Sirius showed. As he was leaving, he wondered how Hagrid got there first...