Tim McGraw
This celebrity is actually the secret child of another celebrity. Raised by Betty Smith, it wasn't until 1967 that singer-songwriter Tim McGraw learned that his father, Horace Smith, was not his biological father. At age 11 he discovered that Horace was not his dad, but it was actually a professional baseball player, Tug McGraw. The player abandoned the family after learning that Betty was pregnant. The two didn't begin a relationship until Tim was 18.