George III, King of Great Britain from 1815. He married Charlotte Sophia 1761 (Pricess of Mecklenburg-Strelitz). However, four of five years earlier he is said to have had a daughter by Hannah Lightfoot, a Quaker, and to have married her. No confirmation though.
No, George III was king from 1760 to 1820 (although his son ruled as regent during his so-called madness). And his marriage to Hannah Lightfoot *is* confirmed by the Public Records Office ...