Billie Jean King believes Caitlyn Jenner has given people clarity about transgender issues beyond the progress already made four decades after they shared the international sports spotlight.
"The interview with then-Bruce Jenner, and now Caitlyn Jenner, really helped people to be clear in understanding, especially about gender vs. sexuality," the 71-year-old former tennis star said in an interview with The Associated Press. "Everybody's always getting very confused with that. Then they finally realized they have nothing to do with each other."
King won the last of her 12 Grand Slam singles titles at Wimbledon in 1975, a year before Bruce Jenner earned the unofficial title of "world's greatest athlete" by winning gold in the decathlon at the Montreal Olympics.
Jenner, 65, publicly transitioned from Bruce in an interview with ABC's Diane Sawyer in April to Caitlyn on the cover of Vanity Fair this week.
"I am so happy he's finally going to be comfortable in his own skin; finally Caitlyn will be," King said. "It's been a long journey for Caitlyn, and I'm really happy for her."
King occasionally traveled in the same circles with Jenner, given they were two of the most recognizable athletes in the 1970s.
"He was amazing when he won the decathlon, so I would run into him every so often," King said. "We actually did a commercial together, but I don't think they ever showed it."
King was 29 when she defeated former professional tennis player Bobby Riggs, 55, in the famed "Battle of the Sexes" match in 1973, putting gender issues in the spotlight.
She later helped pros accept a transgender player in their ranks after she started the Women's Tennis Association in 1973.
Renee Richards, who was denied the opportunity to play as a woman in the 1976 U.S. Open, was born Richard Raskind, a former captain of the Yale tennis team who had sex reassignment surgery.
The New York Supreme Court ruled in Richards' favor, allowing Richards to join the women's pro tour in 1977.
King said she called the players together after meeting with Richards for four hours and receiving confirmation from doctors that she was a woman.
"I said 'We're going to have her on the tour, so get used to it.' Some were unhappy, some were trying to figure it out. But it worked out fantastic," King said. "The players ended up loving Renee."
King played doubles with Richards, who reached the U.S. Open women's doubles finals in 1977 with Betty Ann Stuart. Richards, who was also a renowned ophthalmologist, later coached Martina Navratilova and "really improved her backhand," King said.
King marvels at how attitudes about sexual identity have changed since the early 1970s.
"Being educated, learning, having knowledge is so much better," she said. "Usually things become less shame-based the more you know. An unknown is what people usually fear the most."
Richards is still King's eye doctor and "One of the best people I've ever known. She's been a great role model."
While Richards fought through the courts for acceptance, Jenner introduced Caitlyn via Twitter and was immediately named the recipient of the Arthur Ashe Courage Award for the upcoming ESPY Awards on July 15.
King, who was outed as a lesbian in 1981, won the award for individual contributions that "transcend sports" in 1999.
"Caitlyn's in for a whirlwind. She already has been, but it's going to be crazy," King said. "I think it's really appropriate that Caitlyn's won the Arthur Ashe Courage Award."