09/13/2012 01:13 pm ET Updated Oct 08, 2012

Paralyzed Identical Twins Kirstie and Catherine Fields Speak With American, Australian Accents Through Machines

Kirstie and Catherine Fields, 18-year-old paralyzed identical twins from Wales, have dazzling smiles that belie a steely determination to live life to the fullest. That includes letting the world know how they feel.

Thanks to electronic machines that recently restored their speech, Kirstie communicates in English with an Australian accent and Catherine in an American accent. That way people can tell them apart -- and discover which one has the cheekier sense of humor.

"Already I can say things I’ve wanted to say for a long time," Kirstie explained in a new "O'r Galon (From the Heart)" TV documentary reported by many outlets. "One of the first questions I asked was, ‘Mami, do you and Daddy still have sex?' "

The devices are similar to the one Stephen Hawking uses, the Mirror reported. But the machines didn't have Welsh, the twins' native tongue, as a language option.

The two are the only known sufferers of the disease named after them -- Fields Condition. Their bodies are wracked daily by hundreds of painful muscle spasms, and there is a "strong possibility" they will die young, WalesOnline wrote.

"It's not this affliction that makes my beautiful daughters unique," their mother Lyn once told the BBC. "It's the way they carry on without a hint of self-pity." The 2005 story chronicled how the girls showed difficulty walking by age 4. By 11, they were using wheelchairs. By 14, they could no longer speak. Doctors are stumped.

The documentary (preview below) shows the two being given the speech machines as 18th birthday gifts, courtesy of the National Health Service. They also got matching butterfly tattoos.

"Before this, their feelings were stuck within their heads," their hospice worker, Hayley Mason, told the S4C TV website.

The girls talk about what most teenage girls talk about: boys, sex, love and rock stars, wrote the site. "They can argue and quarrel with each other now," their mother said in the film. "They can sit there and just have chit-chats."

But both sisters used the documentary to deliver a far more powerful message. "Don't feel sorry for us, life is too short," they told S4C. "No one lives forever. Be happy and smile."