On Saturday afternoon, Kate Middleton was joined by her new sister-in-law in the royal box at Wimbledon. The women arrived early to watch the men's semifinals before the long-awaited women's final, where Meghan Markle's close friend Serena Williams will play Germany's Angelique Kerber. As patron of the All England Lawn Tennis and Croquet Club, the Duchess of Cambridge is a frequent attendee of the tennis championship. Kate's family are all big tennis fans, and we've already seen her parents and her sister Pippa and brother James at this year's event. Meghan, meanwhile, had her own important reason to attend, as her friend (and royal wedding guest) Serena was one of the finalists.