As far as I know, there is no known family relationship between Shania Twain and Mark Twain. Shania Twain, whose real name is Eilleen Regina Edwards, is a Canadian singer and songwriter known for her country and pop music. Mark Twain, whose real name is Samuel Langhorne Clemens, was an American author and humorist famous for his classic novels such as "The Adventures of Tom Sawyer" and "Adventures of Huckleberry Finn."
While both individuals have the surname "Twain," it is likely just a coincidence. Surnames can be quite common, and many people who share the same last name are not necessarily related to each other. Without any documented evidence of a family connection, it is safe to assume that Shania Twain and Mark Twain are not closely related or part of the same family lineage.