Oracene Price, the mother of Serena and Venus Williams, says she is surprised her daughter Venus is still playing, considering that she is battling the autoimmune disease Sjogren's Syndrome. Venus and Serena won their 13th Grand Slam doubles title together Saturday at Wimbledon, their first title since Venus was diagnosed with the disease.

"Yeah, I am,” Oracene said. “You know she’s out there and can’t lift her arms and stuff. It’s determination. I know part of this is she wanted make it to the Olympics. After that I have no idea. I think she needs to get it out of her system."

Serena's sister Isha said that Venus is taking inspiration from Serena, who suffered a life-threatening pulmonary embolism in 2011 and won the Wimbledon singles title on Saturday.

"Serena is an inspiration because if she can do that and she was on her death bed and I'm not dying, I do have a disease that I'll have the rest of my life but at the end I can do it too," Venus said.

Over the years, Venus has played the role of the older sibling and has often put Serena’s needs ahead of hers, but Serena says their  relationship has changed to where she’s more supportive now.

"I have to be more supportive,” she said. “She's so strong. I can't imagine what she lives through every day. She's an incredibly strong individual. Not only do I feel like I have to be more supportive, I've always been pretty supportive, but I also feel like I have to be really understanding even more so."