Question: Which sports is Alex O'Brien and Marc Rosset related to ?

Context paragraphs:
1994 Volvo International – Singles: Andriy Medvedev was the defending champion but lost in the quarterfinals to Marc Rosset.

1995 Open 13 – Singles: Boris Becker defeated Daniel Vacek 6–7, 6–4, 7–5 to win the 1995 Open 13 singles competition.  Marc Rosset was the champion but did not defend his title.

2001 Open 13 – Singles: Marc Rosset was the defending champion but lost in the second round to Julien Boutter.

1995 Grand Prix de Tennis de Lyon – Singles: Marc Rosset was the defending champion, but lost in the first round this year.

Marc Rosset: Marc Rosset (born 7 November 1970) is a former professional tennis player from Switzerland who is best remembered for winning the men's singles gold medal at the 1992 Olympic Games.  He also won one Grand Slam doubles title at the French Open in 1992 partnering compatriot Jakob Hlasek.

1993 Grand Prix de Tennis de Lyon – Doubles: Jakob Hlasek and Marc Rosset were the defending champions, but Rosset did not participate this year.  Hlasek partnered Michiel Schapers, losing in the first round.

2001 Milan Indoor – Singles: Marc Rosset was the defending champion at the Milan Indoor tennis tournament but lost in the second round to Greg Rusedski.

Alex O'Brien: Alex O'Brien (born March 7, 1970 in Amarillo, Texas) is a retired professional tennis player from the United States, who competed on the ATP Tour.  He became the world No. 1 doubles player in May 2000 and was ranked as high as world No. 30 in singles in June 1997.

1991 Grand Prix de Tennis de Lyon – Singles: Marc Rosset was the defending champion, but lost in the first round this year.

1994 Waldbaum's Hamlet Cup – Singles: Marc Rosset was the defending champion, but lost in the second round to Renzo Furlan.

Supporting paragraphs: Alex O'Brien Marc Rosset
Answer: tennis