Kirstie was nine when she first spotted Lyle, 13, at a wedding. A few years later, the pair bumped into each other at a funeral, and when sparks flew, they decided to stay in contact.



Although the teenagers were strongly attracted to each other, the couple did everything they could to hide their blossoming romance. Kirstie and Lyle knew their family might not accept them.

After all, they were first cousins.



“I didn't know at the time that it wasn't illegal,” says Kirstie on SBS’s Insight, “so I tried to push the feelings aside and pretend that they weren't there.”



Although Lyle kept it under wraps from the rest of the family for many years, he tells Insight's Jenny Brockie he was always comfortable with the feelings he had for his first cousin.



“I didn't really have an issue with it whatsoever. I was just like yeah, whatever, I'll go with it. She likes me, I like her, sounds good.”

It wasn't until Lyle's mother approved the relationship - and told them it was legal - that the pair decided to go public. When they eventually revealed their secret, the family was shocked.

Lyle’s sister Melanie says she was initially disgusted and still thinks it’s wrong.

“It was just a bit of a kick in the guts really,” she says. “I personally don't agree with it, but because he's my brother, I'm happy for him.”



Kirstie and Lyle now have two healthy children together, but friends and family still find it hard to accept their relationship.

“For our joint side of the family, they all thought it was disgusting, it was wrong. I'm pretty sure after six years they're still gossiping about us,” says Kirstie. “Personally, my father stopped talking to me and I haven't spoken to a word to him in about six years.

"We found that with friends, it's kind of like, you tell them and all of a sudden there's something wrong with you. You've grown a second head. All of a sudden you're not who you were.

"You can't help who you fall in love with. Lyle was the one I loved and that's who I wanted to be with, plain and simple."

Across Australia, cousins are having relationships, marrying and having children together. It’s legal but remains a taboo for many people.



In the Middle East, Africa and Asia, however, cousin marriages (or consanguinity) are widely practised and seen as a way to maintain family and community stability and reduce uncertainties of hidden financial or health problems.



“In Buddhism the Tibetans avoid cousin marriage absolutely,” says Genetics Professor Alan Bittles from Murdoch University, "whereas for Buddhists in Sri Lanka, South India, South East Asia, cousin marriage is very common.



“But I think the important thing with Western culture as well is that until the middle of the 19th century, first cousin marriage was regarded as being terribly romantic. All the English novelists were writing about ‘dearest cousin’ and this was a wonderful idea.



“And then within a ten, twenty year period, the whole mood just changed,” he tells Insight. “At that point in time people started asking questions about possible medical and health problems that would come up.”

In every pregnancy, there is a two to three per cent risk that a child, from two unrelated people, will have a birth defect or disability.



However, that risk will double to about five to six per cent when the parents are first cousins. People who are blood relatives share a greater proportion of the same genes than unrelated people because they have a common ancestor (such as a grandparent). Therefore the risks of a child inheriting a faulty gene are higher in cousin marriages.



A recent longitudinal study in the U.K. city of Bradford found that cousin marriages accounted for almost a third of all birth defects in the 11,396 babies studied.



Medical risks of first cousin marriages include higher rates of infant mortality, birth defects, learning difficulties, blindness, hearing problems and metabolic disorders.

So how are couples and families dealing with this? And can genetic testing help predict any health risks?



This week on Insight brings together cousin couples, their families, doctors and geneticists to find out why cousin relationships are both celebrated and scorned.

Catch the Insight discussion tonight at 8.30PM on SBS ONE or live stream http://www.sbs.com.au/insight/live

What do you think about cousin couples? Share your thoughts in the comments below.

WATCH A PREVIEW



Burak Haliloglu says he's feeling under pressure from his mother to marry a cousin back in Turkey. Burak's parents are first cousins once removed. Although Burak says he respects his parents' relationship, he doesn't want to enter a relationship with a blood relative.