The Lockhart family are well known to live in the Lanarkshire area of Scotland. Mainly in Carnwath, Carluke, and Lanark.
Look up Milton Lockhart, Lee Castle, Hallbar Tower, and Mauldslie to find out more information about the Lockharts.
My friend is Lockhart who originates from Carluke but as far as I am aware he doesn't know much about his family tree.
Good luck with your search.