Father's Day, and stars can't help but celebrate. Celebs like Khloe Kardashian, Michelle Obama, Jenna Bush Hager, Willow Smith, Meghan McCain and more took to social media on Sunday to send love to the dads in their lives. Kardashian took the opportunity to honor her late father, Robert Kardashian, as well as her former stepfather, Caitlyn Jenner, on her Instagram Story.