Now it gets more confusing. In 1900, Mamie Clements is listed as 17, single, and a cousin to James Marlow. Beneath her is Andrew Clements, 81, single, listed as uncle to James Marlow.
I know they made a lot of mistakes on the census back then. And they might have been trying to cover up the fact that they were married when she was a young teen and he was elderly. But if at the time of marriage she was 15 and he was 61 or so, then their ages are way off on the 1900.