While Smith was no stranger to making headlines in Hollywood, Birkhead says she was able to keep a few secrets to herself. He reveals that she was hiding something big in 2006 during her Supreme Court victory regarding her late husband J. Howard Marshall's inheritance.
"She went up [to court] and she wore this big, black trench coat and she got a new black dress," he remembers. "And no one knew she was pregnant [with Dannielynn]. She was laughing inside and thinking -- we were laughing about it saying, 'No one knows.'"
Although Birkhead claims Smith "100%" knew he was the father of Dannielynn, Smith named her attorney and former partner, Howard K. Stern, the father on her daughter's birth certificate.
But following Smith's death in February 2007, Birkhead had a victory of his own when he won the paternity battle against Stern and a few other men after taking a DNA test and proving to the court that he was, indeed, Dannielynn's father.
"One of the things that no one has ever seen before is my actual DNA test that I got when I was holding it up outside the courtroom," Birkhead says. "The judge said I couldn't show anybody at the time, I remember that moment well, so I had it rolled up. 'Yup, it says you are 99.99999999 percent.'"