TO all their neighbours, Cristina and her boyfriend were like any other regular couple - they enjoyed date nights together, were wildly attracted to each other and seemed, from the outside, like the perfect match.

But they were hiding a huge secret - not only were they lovers, they were brother and sister.

10 Cristina has helped other incest couples including Steven Pladl, pictured, who married his daughter

Reunited as adults after being adopted as babies, Cristina and her brother - who are keeping their identities secret for fear of prosecution - fell for each other.

Incest is illegal in the US, the UK, and throughout almost the entire world - but some states have harsher penalties than others, such as Montana, Nevada, Michigan and Idaho, where incestuous couples could face life in prison.

It also poses huge genetic risks to those conceived by blood relatives, with studies suggesting that as many as 40 per cent of children whose parents are immediate blood relatives are born with serious medical conditions.

To hide their controversial love, Cristina and her brother moved across America and settled in a state where nobody knew they were related, although they don't personally see any trouble with incestuous sexual relationships.

10 Cristina and her brother have to keep their identities secret because they fear they could be prosecuted Credit: STOCK IMAGE

In an exclusive interview with Sun Online, Cristina, 36, says: "As long as everybody is a consenting adult, they should be able to do whatever they want to do in their own bedrooms - it's up to them how they want to live their lives.

"Lots of people believe incest is wrong but it's only wrong because it is illegal, but there are lots of things that are illegal now that won't be in a few years."

Since she started dating her brother, legal secretary Cristina has been campaigning to help people around the world who are in sexual relationships with their blood relatives - including a double murderer who had a baby with his biological daughter.

She also believes that related couples should be allowed to have babies, despite numerous studies showing that children of incest are significantly more likely to be born with deformities or disabilities.

Illegal love with her 'soulmate' brother

Cristina has had to change her name, and asked not to be pictured because she fears that she and her brother could be jailed under incest laws.

However, she doesn't agree with these laws, saying: "You can't say something is wrong just because it is illegal - because laws change all the time.

"There are already laws to protect children and vulnerable people: there are rape and sexual battery laws and I don't think incest should be included in that."

10 Cristina says related couples should also be allowed to have kids together

Cristina said it wasn't an instant attraction when she first met her long-lost brother after being reunited as adults, but over the weeks that followed she started to develop feelings for him.

"It took a few weeks - it was like getting to know any other stranger," she revealed. "I remember feeling really confused at first - like why am I feeling like this towards my brother?

"Then he began dropping little hints about liking me and I caught on.

"I told him it's best to be honest and assured him nothing would change and then he just kind of blurted it out. And I told him, 'I've been feeling it too'."

10 Pladl, pictured, ended up killing his daughter, his baby and himself in a triple murder-suicide

Cristina claims that the many physical similarities between her and her brother made them more attracted to each other, saying: "I did begin to notice how much we looked alike. We had the same everything; same eyes, hair colour, cheekbones, lips, nose – even the same hands and same feet."

Cristina is unapologetic about her love, saying many people in incestuous relationships describe their partner as their "soulmate".

"I think there's definitely more of an emotional connection than a regular couple," she says.

"You have the family dynamic and also the adult dynamic - the attraction - so it just makes it different."

The incest case which ended in a horrific murder-suicide

Cristina says she has helped high several high profile incestuous couples come to terms with their feelings.

The people she's offered support to include Steven Pladl, 45, who married his biological daughter Katie, 20, and had a baby with her, before shooting them both in a horrific murder-suicide earlier this year.

Katie, who had been adopted as a baby, went to live with her biological parents in 2016 after tracking them down on social media.

But when Pladl separated from Katie's mother, he started a sexual relationship with Katie. The pair married in secret and had a baby together, before eventually being arrested and forced to live apart.

10 Katie was just 20 when she was murdered by her dad, who was also her husband

Just two months later, Pladl suffocated his seven-month-old baby at his home, drove to Connecticut where he shot Katie and her adoptive father and then drove to New York where he turned the gun on himself.

But Cristina claims that the devastating murder-suicide could have been prevented if people had been more understanding towards the eventual killer, Steven Pladl.

Cristina says that Pladl was "smeared" by society, and that she "felt horrible" for him and his daughter and wife, Katie.

“I’m not making excuses for him but it’s a real shame it got to the point where he did what he did," she says.

10 Cristina also helped mum Monica Mares, pictured, who fell in love with her son Caleb

'My son is the love of my life'

Cristina also helped organise legal representation for a mother and son couple who were arrested last year in New Mexico on incest charges.

As with many incest cases, Monica Mares, 38, and son Caleb Peterson, 21, were reunited as adults after he had been adopted as a baby.

The pair fell “madly in love” and lived together before they were both arrested on incest charges and faced 18 months in prison back in 2016.

In interviews at the time, mum-of-nine Monica told how Caleb was the “love of her life” and how nothing could come between them - even jail.

10 Caleb and mum Monica were arrested on incest charges in New Mexico

The condition which leads to incestuous love

Cristina says these cases, and her own incestuous relationship, were caused by a condition known as Genetic Sexual Attraction or GSA.

GSA is the term for an overwhelming sexual attraction which develops between close blood relatives who were separated at a young age and then meet each for the first time as adults.

Studies have shown that up to 50 per cent of reunions between immediate relatives who were separated at birth result in obsessive emotions.

“We know from studies that the majority of people are attracted to people who have similar features to themselves," Cristina adds.

“So when you think about how siblings who did not grow up together meet and they look similar, have similar interests, have similar dislikes - of course it’s likely they’ll be attracted to each other.

“They have so much in common - it’s what everybody dreams of - this is their perfect match.

“There is no 'ew factor' - the feeling of ‘that's my family member I don't want to even think about that'."

10 Incest is illegal in 50 states in the US and anybody caught can be jailed

Cristina believes that incestuous couples should be allowed to get legally married and enjoy the same legal rights as non-related couples.

She says she and her brother - who have now split up for “typical” reasons that were nothing to do with being related - missed out on many of the things other couples take for granted such as having a wedding.

Cristina even thinks that she should have been allowed to have children with her brother if she'd have wanted, despite the serious and well-established dangers to the baby's well being.

Life-threatening diseases from incestuous parents

However there are huge risks for any children the pair might have had.

Dr Carol Cooper tells Sun Online: “The main problem with blood relatives having children is that it vastly increases the risk of serious genetic conditions, including cystic fibrosis and rare but life threatening diseases like Niemann-Pick and Tay-Sachs disease.

“The latter two have recessive inheritance, meaning that carriers don’t have any symptoms and they don’t know they’re carrying the disease.

10 Dr Carol Cooper says that incestuous parents increase the risk of serious genetic conditions for children Credit: News Group Newspapers Ltd

“However, when two carriers conceive a baby together, the child has a high chance of contracting the disease. You often find that some of the more serious diseases are recessively inherited, which is why it’s not a good idea for cousins to conceive children together.”

Cristina, who is now in a relationship with a man who isn’t a family member, runs a website called Lily's Gardener and a support forum which offers emotional and practical support for incest couples.

She says the forum has hundreds of members from all over the world - including the UK.

10 Cristina runs a support website for people in incestuous relationships called Lily's Gardener Credit: www.lilysgardener.com

Cristina, who lives on the east coast of America, also believes that with the increase of sperm donors the issue of GSA and incestuous relationships will only grow - and she hopes society will become more understanding of GSA.

"I'm not saying these people need to go shout it from the rooftops but they should be able to live without fear of prosecution,” she says.

"There's plenty of things that I know don't like the thought of - for example I would never do anal sex. I think it's the most disgusting concept in the world. But just because I don't want to do it doesn't mean that I'm going to say, 'Oh, you shouldn't do it either.' If you like it, I love it, it's your life, whatever you enjoy.

"Just because I like something I'm not going to force you to like it. But you don't need to report me to the police just because you don't like what I'm doing.

“Is this the kind of world that you would leave in or want to live in? Because that's the kind of world you are forcing us to live in.”

Other recent stories concerning similar cases include the Dad and daughter who were charged with incest after ‘baby they had together’ dies in hospital and the dad who fathered THREE of his own daughter’s children.