Editor's note: Read an excerpt from "My Brother My Sister."
(CNN) -- Molly Haskell will always have brotherly love for Ellen Hampton. After all, Hampton was once named John Cheves Haskell Jr. and used to be Haskell's brother.
Until 2005, Hampton lived as John -- or, as his family called him, Chevey. That year, he told his sister he had been living with gender dysphoria, which the American Psychiatric Association defines as "a marked incongruence between one's experienced/expressed gender and assigned gender."
"This was my 59-year-old brother," Haskell said of the revelation in a phone interview. "He had been this little boy, and all my memories had been of a male. It makes you revisit your whole past."
Haskell details the experience with a critical but compassionate eye in her latest book, "My Brother My Sister."
At the time of the announcement, Chevey was married to a woman, Eleanor, and a loving stepdad to their two children.
Hampton, now divorced, lives as a heterosexual female after gender reassignment and facial reconstruction surgeries, hormone therapy and a wardrobe overhaul.
Haskell recently spoke to CNN about her own familial and emotional journey with her transgender sibling. The interview has been edited for clarity and brevity.
CNN: You've obviously come to terms with Ellen's decision. What did it take on your part?
Haskell: First of all, I realized very soon that it's very overwhelming. I knew I could never say 'don't do this.' My brother would have never hurt anyone, so it really told me how powerful the feeling was. Watching her go through it and evolve -- not only was she radiantly happy, but she was completely upfront with it. Seeing how she handled it -- she would talk about it if people wanted to -- showed me this was meant to be.
CNN: Yet, you do candidly write about having unexpected anxiety about the news.
Haskell: I was afraid for her. I was flabbergasted that this was going on. There was shock and apprehension. I had been all for more diversity, and challenging binary roles for male and female behavior, but it didn't somehow include my brother changing sexes.
The one thing is that we are born male or female, and we need those boundaries to rub up against. I think one interesting thing a feminist said to me is that I seem to embrace these binary principles in the book. I do believe there is such a thing as a male and a female; we need these dichotomies, like good and evil. We make these divides to keep our footing in the world.
The sex we're born is not immutable, and that is very hard to grasp. You can't really call her decision a choice. It's too painful, too perilous, it has to be an urge that we don't even have a word for.
CNN: What was your takeaway from Ellen's journey?
Haskell: I think a lot of people who are transsexual emphasize the strangeness of it all. For example, the director of "The Matrix" Larry Wachowski, who is now Lana Wachowski, has this wild red hair. My sister is so not like that. This book is an attempt to "unweird" the whole subject. I think it's more unnerving to people when the person does just seem so normal, but I do think we have to remember that it's not that many people.
So much changes, but so much doesn't change. You can take hormones to change this, have surgery to change that, but you can't change the voice, the hair, the love -- there is a core of self that doesn't change.
CNN: How has it been different to have a sister rather than a brother?
Haskell: It's wonderful. It's like I've gotten two for the price of one. We have differences -- it takes so long for her to get dressed! We're just much closer than we've ever been. It's hard to say the change hasn't made her happier.
At first I thought I'm really losing a brother. It was like a grief; a death. But, her happiness is crucial. She's more open, more gregarious. I think my mother would've been very, very upset but, in a funny way, Ellen is the kind of person my mother wanted Chevey to be.
CNN: How was it different at age 59 than it might have been earlier?
Haskell: I think the reason she didn't go through with it before is because there was no acceptance. Why is so much of this happening now? Because it can. There is a word for it and there are people doing it. This submerged desire finally had a means of being liberated.
CNN: Having Ellen in your life took some adjusting, even in small areas like the correct language, right?
Haskell: The first time we went out in public, I was very self-conscious and nervous. We went to dinner at an upscale restaurant and the waiter asked how we liked our food. I said, "Mine is good, but his is fabulous." She (Ellen) smirked and I smirked.
I would often call her Chevey by mistake when it was just the two of us. And on the phone, the voice is a huge thing that is not improvable. There is no good surgery. When she gets on the phone, I would see her as Chevey, my brother.
Recently, though, I've stopped doing that. It's automatically Ellen.
CNN: Ellen initially didn't want you to write the book, but then she changed her mind. Why?
Haskell: She wished she had this book when she was struggling with it. I wanted it to be her book as much as my book. I think of it as a partnership.