ON SERENA: Dress, Max Mara ($1,150). Americana Manhasset, 2060 Northern Blvd.; maxmara.com. ON VENUS: Dress, Max Mara ($650). Americana Manhasset, 2060 Northern Blvd.; maxmara.com

When your sister is one of the greatest tennis players of all time, it can be difficult to get together with her for a little family time. When both you and your sister are world-caliber tennis stars—Olympic gold medalists and past US Open champions—it is nearly impossible. But when Venus, 31, and Serena, 29, find that time, it is filled with silliness and laughter, an easy, familial banter as quick as their on-court volleys. As the US Open approaches, both women are keen to hoist another trophy at center court in Arthur Ashe Stadium while at the same time laying the groundwork for their post-tennis careers, including college degrees, charity initiatives, an interior design company, fashion collections and the rightful ownership of a little dog named Harold—or is that Jerry?

  Blazer, Comptoir des Cotonniers ($225). 155 Spring St., NYC; comptoirdescotonniers.com. Bikini top, Nike ($36). nike.com. Pants, Calvin Klein ($79). Bloomingdale’s, 1000 Third Ave., NYC; bloomingdales.com

VENUS WILLIAMS: Tell me about your summer—your wonderful comeback at Wimbledon, and how you feel leading up to the Open.

SERENA WILLIAMS: I’ve been working out a lot since the summer and was really disappointed at Wimbledon, even though I shouldn’t have been. I felt like I should be really happy, but I am never really happy unless I’m on the top. Ever since then, I dedicated myself to working out, practicing more and just trying to do the right things on the court. I had to get serious about my fitness because I have taken so much time off, I almost forgot how to play.

What is your outfit going to look like at the US Open? I know you have been wearing a lot of lace, like you did at Paris last year and at Wimbledon this year. It has influenced my Home Shopping Network collection; we had a tremendous amount of lace. So what is the next trend?

VW: The US Open this year is all about the little black dress, and I always put zippers in my dresses, so there will be a zipper down the back. Because I don’t ever wear black in the daytime, it will be opposing colors. Last year there were three different styles; this year it will be simple because it is just one, but in different colors.

SW: Are you ever going to redo the Wimbledon outfit? That one was probably my favorite.

VW: That’s interesting, because I think people either loved that one or they hated it. I loved the idea, but when it actually got made, I really didn’t want to wear it. I didn’t even like it until you said you loved it, and then I felt confident to wear it.

SW: Will Harold, your dog, be coming to the Open?

VW: [Laughs] I’m glad you said Harold, my dog.

SW: Also known as Jerry, my dog.

VW: Harold always comes to the Open, but he doesn’t know it’s a tennis tournament. He’s just there for the nap. Tell me some of your first memories at the Open.

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