Kate Middleton, Prince William Surpass 500K Subscribers On YouTube Weeks After Official Launch KEY POINTS The couple usually shares clips of themselves on other social media platforms Kate and William celebrated their 10th wedding anniversary in April Kate Middleton and Prince William proved how popular they are after they garnered a significant number of subscribers on YouTube. The Duke and Duchess Cambridge surpassed 500,000 subscribers Wednesday on the popular video-sharing platform, just a few weeks after they launched their official channel. It was not long ago when Kate and William followed the footsteps of Queen Elizabeth II and Sarah Ferguson, who previously launched their YouTube channels.