Aidan and Brenda

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Bonnie's first steps in her sexual transition were changing her name to Aidan and beginning testosterone treatments. Aidan's body fat shifted, his menstrual periods stopped and his voice changed. Having his breasts removed, Aidan says, was the point of no return. "[It was] pretty shocking to walk out into the world for the first time without my shirt. It's kind of liberating." For now, Aidan has decided not to have surgery to construct a penis. "There's a lot of reasons," he says. "It's not cheap. I don't want to risk...messing anything up."

For Brenda, Aidan's sex change challenged her own identity. "It was very emotionally difficult," she says. "I'm an identical twin. Can you take that away from somebody?" But Brenda soon realized that even though Aidan's outward appearance was different, their special bond would always be the same. Brenda now looks at the bearded man sitting next her and sees only her much-loved twin. "Do you [still] feel identical?" Oprah asks. Brenda smiles and answers with conviction, "I feel absolutely identical."