Kerry Washington divulged Monday the long-kept secret that her dad is not actually her biological father, a fact the actress herself only became aware of in recent years, she told People. The revelation is described in her upcoming memoir Thicker Than Water, set to release Tuesday. Washington said she was preparing to appear on Finding Your Roots—a show that makes use of DNA testing to allow celebrities a greater understanding of their ancestors—in 2018 when her parents finally decided to share with her their use of an anonymous sperm donor. “It really turned my world upside down,” Washington told People. “I didn’t know what my story was, but I was playing the supporting character in their story.”