At their home in Leipzig, Patrick Stuebing and Susan Karolewski are in the kitchen, playing with a young toddler.
They share a small flat in an east German tower block on the outskirts of the city. It looks like an ordinary family scene, but Patrick is Susan's brother and they are lovers.
Patrick, who is 30 years old, was adopted and, as a child, he lived in Potsdam.
He did not meet his mother and biological family until he was 23. He travelled to Leipzig with a friend in 2000, determined to make contact with his other relatives.
He met his sister Susan for the first time, and according to the couple, after their mother died, they fell in love.
Patrick and Susan have been living together for the last six years, and they now have four children.
All but one of the couple's children have been taken into care
Incest is a criminal offence in Germany. Patrick Stuebing has already served a two-year sentence for committing incest and there is another jail term looming if paragraph 173 of the legal code is not overturned.
The couple's lawyer, Endrik Wilhelm, has lodged an appeal with Germany's highest judicial body, the federal Constitutional Court in Karlsruhe, in order to overturn the country's ban on incest.
In 2004, Patrick voluntarily underwent a vasectomy.
"It's legal for the couple to live together, and to share a bed. But they are breaking the law once they have sex. If there are no more children, then who will be able to prove that they are a couple?" asked their lawyer.
Dr Wilhelm said a ruling was expected in the next few months.
"Many criminal law experts say that we are right and I'm confident that my clients will win their case. The law against incest is based on very old moral principles. The law was abolished in France, it's about time it should be scrapped here in Germany as well."
http://news.bbc.co.uk/2/hi/europe/6424937.stm
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