Extraordinary life ... Ronnie, left, and Donnie share a home in Dayton, Ohio
The tots, joined at the torso, were not expected to survive the night as baffled doctors tried to work out if they could be separated.
Now, at 57, Ronnie and Donnie are the world’s oldest conjoined twins and have amazed the medic world by hanging onto life for so long.
And, as their health declines and they near their dying days, the pair have opened their doors to a documentary team to reveal the secrets of their extraordinary life together.
Although every day is a struggle as the men have to coordinate the simplest of tasks, they have a close, loving relationship and are able to live together in their own home in Dayton, Ohio.
The affectionate documentary, Extraordinary People: The World’s Oldest Conjoined Twins on Five on March 18 at 9pm, will bring hope to British mum Lisa Chamberlain who is expecting conjoined twins as it shows it IS possible for the babies to not only survive but to live a happy life.
Ronnie and Donnie’s younger brother Jim says: “They have four arms and four legs to coordinate and that takes years of practice. When they want to move they look at each other - it's not like it's telepathy but they think so much in harmony. It's fascinating.
“For things like shaving, between the two of them they don't really need a mirror, they take care of that by shaving each other’s faces.
“That's what you call a good bond with your twin brother.
“They go out to their favourite diner once a month and everybody treats them normally, as if they are two separate people, which is what they are.
“And they have their own possessions. Even if they look identical, there is two of everything, because it’s important that they keep their own identity.”
The pair have learnt to do all their own household chores using one hand each - and Ronnie even calls Donnie “the little wife” because he is so domesticated.
And though Donnie is scared of the dark, comfort is always close at hand as Ronnie gives him a brotherly cuddle in the bed they share.
But life joined to your twin brother is not always happy.
The pair - who have completely opposite personalities - get so irritated with each other they often have physical FIGHTS.
Jim says: “They don't like the same shows so usually the biggest arguments are over the TV even though they have two now. If one turns the volume up on his TV, the other turns the volume up even louder.
“The last time they got into it, four or five months ago, Ronnie had a shiner.
“They get mad at each other like any other brother, but they can’t go in the other room and cool off. It gets so intense and angry, it usually takes literally four or five days to simmer.
“Ronnie's happy go lucky, no cares in the world. Donnie is very articulate, very hard headed, very stubborn.
“When it finally runs its course, they’ll start crying because it’s over and they’ll both be bawling their little hearts out. One will reach over and kiss the other on the forehead and they've made up. When it's done, it's done.”
Their doctor, Glenn Kwiat, adds: “The closeness that Ronnie and Donnie share is not always a positive. If you think of somebody, even the person you care about most, and imagine you were chained to them 24 hours a day, never being able to get away - their whole life is a compromise.
“I’ll go over there and there’ll be black and blue eyes. I actually had to sew one of them up because the other one had punched him.”
Other problems include the twins’ lifelong desire for a physical relationship with a woman - and even a baby.
Although the brothers have separate hearts, lungs and stomachs, their vital organs join in the digestive tracts - so they have one lower intestine and one set of sexual organs.
Jim says: “They would love to have been able to date and marry and father children, but having just one set of sexual organs, who would be the father? It gets a little quirky, does it not?”.
Dr Kwiat adds: “Their male function has been normal. And that's something that, when they were younger, had to be addressed because they had the normal male urges and the normal hormones. Trying to channel those so they didn't become aggressive or frustrated was an issue.”
When the twins were born, they made medical history. Conjoined twins make just one in 100,000 births. Of those, up to 60 per cent are stillborn.
Ronnie and Donnie were kept in the Saint Elizabeth Hospital for 29 months as fascinated doctors observed and worked out if they could be separated.
But Jim says the chances of Ronnie surviving a separation were thought to be minimal - so, Maureen having rejected the children, their father Wesley was left to make the decision on his own. He decided not to risk it.
He says: “Their lower intestine is one. One penis, one rectum. Donnie has control of that. Therefore if they separate them, Ronnie would have to be reconstructed. And you're talking about the 1950s - that probably wouldn't have been too likely. That decision was made that if they both can't make it, we're not going to proceed with that.”
Wesley was inundated with requests for the twins to star in freak shows - and although he resisted at first, the cost of looking after the boys and their seven siblings soon meant he had to relent.
They had already been banned from schools as teachers said they were “too distracting” for other pupils - so they have never learnt to read or write, one of their biggest regrets in life.
Jim says: “You’d get people parked out the front trying to get a peek at them. You'd get, for want of a better word, curiosity seekers. Understandably, that's something you're not going to see all the time, two people stuck together. That's confounding. But it meant it wasn't a normal life for us.
“My dad had this trailer and Ronnie and Donnie would sit there watching TV and people could pay to watch them.
“People would say, “That's offensive, having them making a living like that”. Well, what are they supposed to do? It's not like they can go out and drive a truck for a living.
“Dad made a living through Donnie and Ronnie, and supported nine kids on that. We're proud of him for that.”
In 1991 Ronnie and Donnie retired aged 39 and bought a two-bedroomed house with the money they made.
Now, suffering scoliosis and arthritis as well as being dangerously overweight, the pair can stand only for short periods and rarely venture outside.
Jim and Dr Kwiat are preparing themselves for the fact Ronnie and Donnie may not survive much longer.
Dr Kwiat says: “When you look at the literature on conjoined twins, when one dies, it's often immediate that the other one dies. But in other cases it can be 17 or 18 hours before the other one dies.
“At that point of life, you’ve been joined to someone your whole life and they’re dead, and you know what's coming. If that happened to Ronnie and Donnie I think you would have to sedate the other one until nature takes its course.”
But however their life comes to an end, there are no regrets for Ronnie and Donnie, who believe they have had a happy life.
Touchingly, Ronnie says: “Our belief is this - let God separate us. Let the good Lord separate us. God made us, let God separate us, not using surgical knives.”