All Leslies are descended from the same Scottish Clan and Great Family, one of the very oldest. Tradition says it began in 1069 A.D. when the Saxon claimant to the throne of England was defeated by William the Conqueror and fled to Scotland. Edward the Atheling, as he was called, arrived there with his mother, a Hungarian Princess, and his two sisters. They were cordially received by the king, Malcolm III Canmore. A year later the king married Margaret, one of the sisters, who became a great queen of Scotland and a saint of the Christian Church. Her Chamberlain, Bartholomew, a Hungarian nobleman, had much impressed King Malcolm who made him Commander of Edinburgh Castle. Bartholomew married Beatrix, the King’s sister in 1070 and thus the family and Clan of Leslie was founded. Bartholomew was granted lands at Leslie in the district of the Garioch, near Aberdeen, originally known as the lands of Lesslyn. It is from Lesslyn that the Clan eventually took its name. The present Leslie Castle, built near site of the first primitive stronghold, recently was completely restored by architect David C. Leslie.
(Copied from the Clan Leslie Society International website. )