Becoming a parent is a life-changing experience. But when Julie and Richard Matthews welcomed their twins Will and Emily, in March 1997, little did they know just how much of a challenge awaited them.

Almost immediately, the couple realised there were marked differences between Emily's development and Will's. Will struggled to latch on with breastfeeding, could not hold his head up at six months and had very little co-ordination.

But, despite Richard and Julie's concerns, it took five years for Will, now aged 21, to be diagnosed with XYY chromosome syndrome - an extra chromosome which left him with severe learning difficulties.

"We've all got 23 pairs of chromosomes," explains Richard, who lives with the family in the village of Chettle, near Blandford.

"Your final pair dictate your sex - XX is a girl, XY is a boy. Will has an extra male chromosome. It affects about one in 1,000 boys, so it's rare, but not unheard of.

"Some of those will never be diagnosed because there are no signs. There's a spectrum - Will is off the end of that spectrum. Will has never managed to read or write, he can't tell the time. Fantasy and reality blur into a magical mystery.

"But I think one of the reasons it was so hard to get a diagnosis for Will was because he was so engaging, so his personality would convince people that everything was okay, he was just being lazy."

Richard, 47, openly admits that raising Will and seeing him struggle has been an enormous challenge for the whole family. But he added that, despite his limitations, Will inspires him every day.

"He is innocence personified and sees the world as the truly wonderful and magical place that it is,"he says.

"He reminds me how to have fun, to find humour in everything and show kindness to everyone."

Will, who has a life-long passion for dressing up in various costumes, including Elmo and Mickey Mouse, became well-known in the small village where the family live, and Richard would often find people stopping him in the street to tell them about things Will had done or said to make them smile.

"When the twins were about 10 or 11, I started on Facebook as a way of keeping in touch with all my best mates," he says.

"For years, it was just holiday photos etc. Then I started to share photos of Will walking round the village in his outfits or funny things he had done. The reaction was extraordinary.

"Over the last ten years I would get phone calls, be stopped in the village by people I didn't know."

This reaction, combined with Richard's desire to share Will's unique outlook on life, led to the idea of him writing a book about the family's journey.

"I had always wanted to write a book," he explains, "I had a talent for writing when I was at school. I was fed up at work, sold some stuff off. I took a massive gamble.

"My goal was to end up with a published book. I took a year off work. As I was going along, the feedback I was getting from those trusted friends was so strong that I started to believe I had something really good here."

The result is No I Will - named after one of Will's own phrases - which was published earlier this year, and is a searingly honest account of Richard's experiences of raising a child with special needs, detailing all the highs and lows of life with Will, who now works at two local community farms.

"Over the years, I struggled with it massively," he says.

"I had met a lot of fathers of children with special needs that never came to terms with it. They really struggled. I've learnt to deal with everything with a sense of humour. He's made me so much more patient, understanding, compassionate. It's a father-son story.

"I've realised that we can't always get what we want in life, but maybe we get what we need. Will brings joy and happiness to everyone that meets him - every family should have a Will."

No I Will, by Richard Matthews is published by ShieldCrest, available now to order from Amazon and from all good bookshops, as well as being stocked in Gulliver's Wimborne.