 Mariah's mother was Ariana Carter, one of Custis's house slaves.When Mariah Custis asked her father for permission to marry Charles Syphax, one of his slaves, he freed them both, held a wedding for them in his Arlington mansion, and gave them fifteen acres of his Arlington estate.Mary Custis (1808–1873), Mariah's white half-sister, was to marry the Confederate General Robert E. Lee (1807–1870).