Reese Witherspoon celebrated Mother's Day on Sunday by honoring her three kids, 17-year-old Ava, 13-year-old Deacon, and 4-year-old Tennessee. The proud mom posted a beautiful family photo on Instagram, along with a heartfelt message about the joys of being their mom. "Being a mom is one of the biggest joys of my life. I have learned so much from my 3 kids... patience, kindness, humility, creativity and of course, how to tell a great knock-knock joke! 😉," she wrote. "To my wonderful kids, I love you more than you will ever know (You will figure that out as soon as you have your own kids. 😘) Always know how grateful I am everyday I get to be your mom!! 💖✨💖." Just last month, Reese celebrated the season finale of HBO's Big Little Lies by hitting the beach with her children.