Harry becomes a Lord of Many and a king!!!

The Potter family was near-perfect, two twin sons, wealth, fame, and a future brighter then the sun... but it hides a secret, while one son the 'older' of the two sons, Charlus, or Charles as his parents called him, was known to have magic, but none had heard anything of the younger, Harry. The reason being very sinister, on that fateful October night, where Godric's Hollow was razed to the ground, there was a choice made, Charlus the supposed 'Boy-Who-Lived' had his core fail after Harry blocked Voldemort's Avada Kedavra. Dumbledore took the two boys, who's parents had then been awakened from their duels with Voldemort, and switched their cores, Harry lost his magic, and Charlus regained his. The switch had been covered up, Harry being said to be a squib, but what if one day, Snape accidently let it slip, not knowing that Harry was eavesdropping? What if he stumbled across the mythical castle of Avalon? What if an old man welcomed him, adopted him? What if that old man... Was King Arthur Uther Pendragon?