CAROLE: When John was small, my brother Andrew and I often looked after him. We did our best to boss him around and keep him out of our way. Once we put him in a cupboard with a bottle of juice for a couple of hours. Then when we saw Mum walking up the street we pulled him out and threatened his life if he shopped on us. At Hallowe’en we’d take him trick-or-treating. John was so cute, with huge dimples and a great smile, and neighbours looked at his face, invited us in and we got a ton more candies. Even then, John was hard to resist and he loved an audience.

When Dad’s company transferred him to the States, we all moved there. But as I was about to start university and Andrew was in high school, John was pretty much an only child — a hugely loved third child, who had more freedom than we’d had. I guess our parents thought: “What the hell… we did fine with the others, let John do what he wants.”

Family relationships shift and change. The age gap between us disappeared a long time ago. And I’m loving my 15 minutes of fame as John’s big sister. We’re incredibly good friends. As soon as something exciting happens in John’s life he’ll call my parents, then me, then my daughter. He and Scott regularly take our kids travelling. I often think: “I wish I had an Uncle John like him.” He phones my parents every day, and he and I have cameras on our computers, so we connect for a chat three times a week.

Over last summer I came to the UK to work on the book while he was filming Torchwood in Cardiff. One day we went shopping together in Tesco. As we ventured deeper into the vegetables, word spread that Doctor Who’s Captain Jack was in the store. By the time we reached the canned goods, there was a crowd wanting his autograph. John gave me the grocery list and told me to get on with it, while he signed away. I was so shocked, I looked at him and said: “You’ve got to be kidding!” Why couldn’t I wait in line while he did the shopping? “Because,” he said, without a hint of malice, “no one wants your picture on their cell phone, and all these people are causing a bottleneck in Aisle Four.” Well, little brothers, famous or not, don’t tell their big sisters what to do. But I realised he was right, snatched the list and stormed into the jams and milk. Next day, near Cardiff city centre, I saw John’s full Torchwood image on the back of a double-decker bus. After the first shock, I announced to an elderly lady in front of me: “Hey, that’s my little brother!”

In any other context, the role of taking care of our parents may have fallen to me, as the oldest child. But because of the man he’s matured into — the person John is — that’s something he sees as his responsibility. It drives him nuts if he sees or hears people abusing or talking badly about old people. Andrew and I are very involved with our parents too, but John’s much more financially sound than we are. My parents get a huge amount of pleasure from his success. And he’s so generous to our children. When my daughter, Clare, got her driver’s licence, he wanted to buy her a car. He could easily have bought one, had it gift- wrapped and delivered to the house but he discussed it with us first. We thought she didn’t need a car. And the insurance payments would’ve been too much for her. So he waited ’til she was a couple of years older before buying one.

John and Scott are fabulous role models to my kids, who’ve never felt any weirdness about their uncle’s sexuality. Being gay is much less of an issue for their generation. Any time anyone has ever said something disparaging about being gay, they’ve both stepped up to the plate and spoken up for the person getting flak. I’m proud of them for that.

When he was at school, John hung out with all the most creative kids and didn’t have girlfriends. And when Kevin and I went to London to see him in a West End show, we said to each other: “For sure, he’s gay.” But it wasn’t an issue. Then in 2003, when Gay Times ran an article about him, he called my parents and then Andrew and me to make sure we all knew the story was going to be public. We all said “Fine” and moved on.

At Christmas, John arrives like a tornado, wanting everyone to have a better time than they’re already having. We all get bigger and better presents, but he’s never forgotten where he came from. My little brother hasn’t changed. He has integrity as a performer and as a man. He’s never lost the ability to laugh at himself. And in our family that’s a biggie.

JOHN: I was an unruly child who didn’t sleep. I got away with murder. My parents joked that if I’d been the first child, they wouldn’t have had any more. Carole and Andrew sometimes had to babysit, and as the oldest, Carole was in charge. One day they took me to the swings near our house in Glasgow. I kept asking to be pushed harder and higher. She pushed me so hard I fell off the swing and cut my lip. Carole picked me up, took me home, shoved crisps into my mouth and got out my dummy. She told Mum I’d fallen over eating crisps. It was only 30 years later, when we were sitting around telling family stories, that she and Andrew owned up.

When Dad told us we were moving to the States, Carole was all set to go to Glasgow University. “I’m not going to America!” she said. And Andrew was about to be signed to Rangers Juniors. I remember thinking how much harder it was for both of them. But it all worked out, and America has been very good to all of us. Scotland gave us the family closeness, America the get-up-and-go.

Carole had been a year ahead at school in Scotland, and she was accepted by every college she applied to. Writing was always her passion, and she won lots of university accolades. She’s written three unpublished novels and screenplays. I’ve just sent one to the BBC. I really want to give something back and help Carole. When I decided to write my book, I realised she was the only person I could work with. I knew she’d honour who I am, and not make something else out of what I said. And I had no qualms in telling her anything. We lived and worked together for three months. She talked on set to friends and work colleagues, and she’d interview me in the car, travelling back and forth to jobs. I’m pretty honest, and she’s been true to that. I’m opinionated and say my piece, but Carole’s never raised an eyebrow. After a couple of months she said to me: “I have a gay man living in my head!” And basically the book reads exactly how I talk.

My niece, Clare, wants to follow Carole into teaching. I’m so proud of the way my sister and Kevin have raised their kids. Clare and Turner are two forward-thinking young people who give unconditional love. I often joke with them: “Think gay and you’ll get it right.” To be honest, gay also means stylish, modern — and, sometimes, funnily enough, conservative.

When the story that I was gay was going to be out in the open, I told Scott, of course, and Mom and Dad and then Carole. I thought my brother would be the hardest to deal with and I didn’t tell him right away. He was upset about that. I’d completely misjudged the situation, but I learnt from it. Carole just said: “Like we hadn’t known!”

My greatest satisfaction would be if another publisher asked Carole to ghostwrite a book for someone else, and wanted to see her novels. I’d love for her success to come out of the book more than mine, because you know what? I’m doing okay. My family have always been there for me. They’d stand on my battlefield at the drop of a hat. Now I want Carole to get a foot in the door.

John Barrowman’s memoir, Anything Goes: The Autobiography, ghostwritten by his sister, Carole, (Michael O’Mara Books, £18.99) is out on January 24

Interviews by Sue Fox.

Portrait by Ivor Prickett

Times recommends

• The pink mile: women on death row
• The top 10 richest streets in the world
• Japan's new professional seducers