Mark Knowles and Xavier Malisse were the defending champions but Knowles did not participate this year because of his retirement from professional tennis in September 2012.
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Mark Knowles (born 4 September 1971) is a former tennis player from the Bahamas, specialising in doubles tennis.
 He has won a number of Grand Slam tournaments, most notably partnering with Daniel Nestor.
 At various times between 2002 and 2005 he was ranked World No. 1 in doubles.
 He is a five-time Olympian.
Mark Knowles and Daniel Nestor were the defending champions, but Knowles chose not to participate, and only Nestor competed that year.
Mark Knowles and Brian MacPhie were the defending champions but they competed with different partners that year, Knowles with Daniel Nestor and MacPhie with Nenad Zimonjić.
Mark Knowles and Daniel Nestor were the defending champions and successfully defended their title, defeating Leander Paes and Nenad Zimonjić 3–6, 6–3, 6–2 in the final.
 It was the 39th doubles title for Knowles and the 41th doubles title for Nestor, in their respective careers.
 It was also the 4th and final title of the year for the pair.
Mark Knowles and Daniel Nestor were the defending champions, but did not compete together.
 Knowles partnered with Mahesh Bhupathi, but lost in the first round to Stephen Huss and Ross Hutchins.
Mahesh Bhupathi and Mark Knowles were the defending champions, but they chose to not compete together this year.
 Bhupathi played with Max Mirnyi and Knowles partnered with Radek Štěpánek.
Barbara Jordan (born April 2, 1957) is a former professional female tennis player from the United States who won the 1979 Australian Open singles title.
Mark Knowles and Daniel Nestor were the defending champions but only Knowles competed that year with Brian MacPhie.
Mark Knowles and Daniel Nestor were the defending champions, but Nestor chose not to participate, and only Knowles competed that year.

Question: Barbara Jordan and Mark Knowles are both what?
Answer: former tennis player