Her mother, Sybil Smith, was a swimmer at Boston University and a member of the school's athletics hall of fame. Her bio on the BU Hall of Fame web page calls her "the finest swimmer in Boston University history."
Her father was John Stephens, who was a Patriots running back for six seasons beginning in 1988. Stephens, who made the Pro Bowl as a rookie, was killed in a car accident in 2009 at age 43.
Sloane Stephens, 19, scored the biggest win of her pro tennis career in beating the top-ranked Williams, 3-6, 7-5, 6-4. It ended a streak of 20 straight wins for Williams.
Stephens faces defending champion Victoria Azarenka in the semifinals.
The Wall Street Journal reported Stephens' Twitter following more than doubled after her victory Wednesday. Boston University even sent a congratulatory message.