HE WAS originally billed as Little Jimmy Osmond, but as anyone who watched I'm A Celebrity, Get Me Out Of Here last year knows, the nine-year-old who famously scored a Christmas No 1 in 1972 with Long-Haired Lover From Liverpool has grown up.

Now 42, the father of four laughs as he admits: "Yeah, Long-Haired Lover was the one that stuck. I didn't even know what I was doing at the time . . . I still don't. All I know is that it's been fun."

Laid-back is definitely the best way to describe Jimmy Osmond, the youngest member of the most famous singing family since the Von Trapps. And he certainly had fun the last time he was in Edinburgh in 2003.

On that occasion, he was making a guest appearance in the Royal Variety Performance at the Festival Theatre, where a rocking performance of Crazy Horses saw the Osmond brothers reunited on stage and had the audience going wild.

"That was the best experience for us because we were all on stage together and the reaction was so immense," he recalls, his face breaking into a big smile.

"It was wild - in fact, it was so wild that they cut a lot of the audience reaction out of the programme, because it wasn't fair on the other acts. We didn't care, we were just in the moment and numb, all there for each other - that's what was so cool."

Ill-health and other commitments mean that when the Osmonds return to the Capital on Sunday it will be a slimmed down line-up that serenades an almost sold-out Playhouse - just Wayne, Merrill, Jay and Jimmy, who explains: "Although we still do all get together, it's becoming harder because everyone has families. So we really don't take for granted the time that we work together.

"This might be the last time that we all perform together, meaning the four of us who continually work together, at least over here, so we are excited about this tour."

Missing from the line-up will be perhaps the most famous Osmond of them all, Donny ("He's touring right now," explains his brother) and Alan, the eldest of the performing Osmonds, who has multiple sclerosis.

"Alan's okay, but not doing great. His attitude is good but his physical situation is hard on him," says the singer. "It's hard for us too because he was always our leader. For him to have something that is so debilitating is hard for us to see."

A guest appearance from the other singing Osmond, sister Marie, on Sunday is also out. "She's doing well and is a mother of eight kids, most of them are adopted," reveals her little brother who, with wife Michelle, cites being a good parent to children Sophia, Zak, Wyatt and Bella as the most important thing in life. Even the music comes second.

"Number one is I'm a dad, which is awesome," he says. "That always takes priority. Anything beyond that has to be a realistic and respectful way of making money to put away for their futures."

Respectful, it turns out, is a very important word in Jimmy Osmond's vocabulary, and one that cost him an acting career - he starred in the 1978 movie The Great Brain and appeared in an episode of The Love Boat and as Troy Phillips in the 80s TV series Fame.

"I really wanted to act, but the really difficult thing I found was that as an actor you are not in control of what you do and you say. For me that was a big issue.

"I was offered some roles and I just couldn't do them because they went against what I really believed in as a person. I envy those people who are actors, but I just can't be something I'm not. I think that if you are going to stand for something you better just do it," says the devout Mormon.

His religion, he agrees, is the point of reference for everything he does and the driving force of his life.

"When you have those quiet times to assess who and what you are and what you believe in, you ask yourself: 'What governs your life?' The answer is what you believe in religiously," he reflects.

If Osmond's upbringing instilled the values by which he lives his life, it is a childhood he has also described as "surreal", in so much as after performing he would go home and play with his pals just like any other kid.

"It was a very happy childhood," he says, denying that, as the youngest of the family, he was protected more than the others.

"In many ways, because I was the last one and everyone was off doing their thing, I had a little bit more freedom than the older brothers," he says.

"They were told what to do constantly and I don't mean that in a bad way, they were just very enmeshed as a group. I always did my own thing and that really benefited me in later life because I always felt I was my own guy. I didn't have to perform with my brothers, I wanted to. Some of my other brothers feel that they missed out because they didn't have their own autonomy."

Surprisingly, while his brothers made a name for themselves performing on the Andy Williams Show, it was Jimmy who was first to release a single.

"I started performing on the Andy Williams Show with my brothers, I would always come and do my own solo and then they'd come and back me up. And then I recorded on my own and had my first hit."

Osmond was seven when he recorded My Little Darling, which he sang in Japanese. Even then he was an old hand, having debuted on the Andy Williams Show when he was just three years old.

Returning to his first single, he laughs as he adds: "That was funny because it was billed 'Jimmy and the Osmonds' and I used to rub it in. But honestly, I have more fun performing with my brothers than I do on my own."

There is far more to the youngest Osmond than performing, however. A shrewd businessman, he now heads a diverse business empire, which covers everything from producing ice extravaganzas to shooting adverts in Japan and illustrating kids' books.

He remains modest about his success, however, and says: "Anyone can do that. I don't give myself that much credit. I think timing is everything. I've been afforded by the hard work of my brothers and myself the opportunities that a lot of people don't get and I don't put that down to anything but blessings.

"I wish I could tell you that I'm really smart, but I'm really not."

Nevertheless, by the age of 15 "Little Jimmy" was already heading the company that developed and supervised much of the Osmonds' merchandising business.

"I used to design a lot of the concert books and stuff," he recalls. "I always cartooned and loved layout and drafting and type-setting. I thrived on putting stuff together. Oddly enough, I can't believe that my parents allowed me to do the stuff I did because I have an 11-year-old daughter myself now and I can't imagine having her do some of that stuff.

"When I was around 14 or 15 I actually had a company. I had people who were smarter than I was who ran it. It was very weird, but also embarrassing because the people who ran the company had to pick me up because I didn't have my driver's licence at the time."

And as he prepares to reacquaint himself with Edinburgh, he reflects that he is surprised to find himself where his is today.

"I really am surprised because although I know I'm a good singer, I'm not the best."

And he promises fans that, despite the group's depleted numbers, all the hits will be there, along with the odd surprise.

"We want to be respectful of what we have done together as brothers," he says, "but I may throw in Long-Haired Lover just for fun.

"Last time we were in Scotland I wore my kilt when I sang it, so you might see that again."

• The Osmonds, Edinburgh Playhouse, Sunday, 8pm, £29.50, 0870-060 1730