Light was seven when he ran away from home. He was seven when he found a panda looking child. Light was seven when he was finally accepted for who he was. L was nine when he became the world's greatest detective. L was ten when he found a brown-haired child covered in dirt. L was ten when he made his first friend. AU: Light runs away from home and is found by L. This follows Light and L growing up together and then the Merikh Case (which follows the timeline of the Kira Case just a different name). Light uses the name of Kira when he is at Wammy's House so hence the rename.