The Whittaker family have a complicated history of inbreeding - and it's left them with heartbreaking genetic defects.
Some members of the West Virginian clan can only communicate through grunts and barks instead of talking and even run away when people try to speak to them.
Living in the village of Odd, which is 75 miles from Charleston, the Whittakers can't remember much about their parents or other family members and didn't know their genetics issues were due to inbreeding.
One of the daughters, Betty, would not say if her parents were related when asked about their background by a documentary maker, but she later confirmed her mum and dad are double first cousins.
The inbreeding started with a set of identical twin brothers, Henry and John Whittaker, whose children got married and had over a dozen kids together.
Henry and his wife Sally had seven children, including John Emory Whittaker in 1913.
While John and his spouse Ada Riggs, who was his own first cousin, had nine kids, including Gracie Irene Whittaker in 1920.
John and Gracie, who were double cousins and shared both sets of grandparents, married in 1935 and went on to have 15 children.
Many of their children had a number of severe physical and mental impairments, which are believed to have been as a result of inbreeding.
Their eldest, Aileen, passed away in June 1997 after suffering from a heart attack, while oldest boy Emery died a month after being born in 1938 after suffering from pneumonia.
Betty, who was born in 1952, has taken on the role of the matriarch of the family and promised her mother she would not marry so she could look after her 14 siblings.
Ray and Lorene, who has a son named Timmy who was born in 1979, are both seemingly unable to speak and can only communicate through grunts and barks.
However, they seem to understand the limited forms of communication they do use, even if it may sound unintelligible to an outsider.
"They understand what you talking about,” a relative said. "If they don’t like it, they start yelling — let you know they don’t like that idea."
Timmy is the only member of the Whittaker clan who has graduated from high school.
A filmmaker documented the lives of the family after first visiting in 2004 finding them living in a cramped shack with several dogs.
Photographer Mark Laita didn't receive a warm welcome when he first rocked up as an angry neighbour threatened him with a shot gun.
The Whittakers neighbours are very protective and chase away anyone looking to taunt them, but Laita managed to win their trust and began a relationship which lasted two decades.
Speaking on the Koncrete KLIPS podcast, he explained that his first impressions of the family were like a scene from 1972 thriller Deliverance.
"We came around to this road, which turns into a country road, which turns into a dirt road, and we come to this trailer and then a little shack on the other side of the road," he explained.
"And there’s these people walking around and their eyes are going in different directions and they are barking at us.
"And then one guy, you would look at him in the eye or say anything and he would just scream and go running away, and his pants would fall around his ankles, and he would go running off and go and kick a garbage can.
"And this would happen over and over. It was out of control - the craziest thing I have ever seen."
The Whittakers eventually allowed him to take some photos after he offered to take a portrait for them to place in the casket of a loved one who had recently died.
"They are kind of protected by the neighbours and the relatives [who] don’t like these people coming to ridicule them," he added.
"And everybody in the area kind of knows of them and are like, 'let's go over to the Whittakers' and laugh at them or whatever.'"
Over the years, Laita returned to visit the family and filmed a documentary in 2020 about their way of life, which has been viewed more than 28 million times.
The documentary film showed him conversing with the three siblings, Betty, Lorraine and Ray, as well as with their cousin, Timmy.
When asked why their eyes don't point forward, another relative, Kenneth, said: "Might be coal mining."
Laita returned in 2022 for another follow-up after setting up a GoFundMe page which has raised $55,000 (£44,000), and discovered that conditions inside their home had greatly improved.
Visiting the family after they received the generous donations, Mark found they had spent the entire sum out on a number of home improvements
They had spent the entire sum on a new truck, roof, kitchen refit and a coal heater.
One of the relatives takes Mark on a tour of their cramped home, where two of the adult men share a single bed and an elderly woman sleeps on a sofa in the living room all year round.
Laita explained that ultimately his goal is to shed light on issues in parts of the country that people seldom see.
"People can say that people in Appalachia are leading these wonderful lives, leave them be," he explained.
"But they could also get a lot more support from the government or corporations or something so they could not be digging up roots in the middle of the winter, climbing mountains to survive on $10,000 a year."
He added: "Despite the fact that they don’t complain, it’s a really rough life."
