Catherine and Kirstie Field are two special sisters. They've lost their mother tongue because of a cruel illness but they'll be communicating with S4C viewers for the first time ever in a documentary on the channel this week.
The 18 year old twins from Bryn near Llanellli are the only two people in the world who suffer from this neurological condition which has already paralysed them and robbed them of their speech. No one knows what the future holds for them, and there is a strong possibility that they will die at a young age.
The illness Field's Condition has been named after them. It affects the muscles of the body, which means that Catherine and Kirstie are paralysed. They suffer from painful spasms daily as their muscles move uncontrollably. There's no treatment for these, all they can do is suffer the pain and wait for the spasms to subside.
But as we see in the film Fy Chwaer a Fi (My Sister and I) - which is part of S4C's documentary series O'r Galon (From the Heart) - the disease hasn't robbed them of their spirit, bravery, intelligence and humour.
The film's producer and director, Mei Williams, followed the girls for eighteen months. It's been a difficult experience. Catherine and Kirstie have used the film to share their feelings with us about their illness, their parents and their lives. They talk about boys, sex, love and marriage, Harry from the band One Direction, and their desire to have a tattoo.
Before their voices disappeared because of the illness, the twins spoke Welsh. After not being able to speak for some time, their new electronic communication machines now enable them to talk and share their feelings with each other and the world. The machines speak many languages but not Welsh. This means that Catherine and Kirstie now have electronic English voices. But at least they are able to communicate.
"That's why they wanted to make this film," says Mei Williams. "They wanted to share their feelings about life for the first time. It's a very moving film as Catherine and Kirstie share every part of their lives with us in their own words."
One of those who appear in the film is Hayley Mason who has been working with the family since the girls started visiting the Tŷ Hafan hospice. She's glad to see them now being able to communicate by using the new machines.
"Before this, their feelings were stuck within their heads. It was difficult for them to explain how they were feeling," she says.
"They are amazing," says Hayley whilst talking about the twins, "and they're always thinking about everyone else and don't complain. They're absolutely delightful girls and I love spending time with them. They uplift you, that's how they make you feel."
And says Kirstie, "The machines have opened up a whole new world for us. I hope this will give you a better understanding of our lives."
"Don't feel sorry for us, life is too short," say the girls. "No one lives for ever...Be happy and smile."
This documentary is being shown again following its success at the New York Festival's International Television & Films Awards 2013. Fy Chwaer a Fi was awarded a World Gold Medal in the Human Interest category. The programme was also nominated in the Single Documentary category at the Royal Television Society Programme Awards 2013.
Press release - http://s4c.co.uk/e_press_level2.shtml?id=762