Jennifer Flavin is celebrating Sophia Stallone's birthday! The mom of three, who recently filed for divorce from husband Sylvester Stallone, took to Instagram on Saturday to mark their eldest daughter's big day. She wrote, "Happy Birthday beautiful Sophia! You bring so much love and happiness to everyone you know! Besides being a Beautiful person, you are hard-working, smart and most of all compassionate. I am the luckiest mom in the world to call you my daughter! Love you!"