Which U.S. President had his sister initially serve as First Lady?

Before marrying Frances Folsom in 1886, President Grover Cleveland relied on his sister, Rose Cleveland, to serve as First Lady during the early part of his presidency. Rose Cleveland was highly educated and intellectually respected, though she was less interested in the social and ceremonial duties traditionally associated with the role. After Grover Cleveland married Frances Folsom at the White House, Frances became First Lady at just 21 years old, making her the youngest and most admired First Ladies in American history.