A German brother and sister, who have four children together are campaigning to have their country’s incest laws quashed.

The two siblings, Patrick and Susan Stubing — who grew up separately — have had three of their children taken into foster care.

Two of the children have disabilities although it is not known if these are due to inbreeding or because they were born prematurely.

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.

The couple’s supporters said the law is archaic and harks back to the Third Reich’s obsession with racial purity. They want Germany to follow the example of countries such as France, Belgium and the Netherlands where incest is no longer punishable.

However, many medical experts defend the existing law. “We need this law against incest in Germany and in the whole of Europe. It is based on long traditions in Western societies, and the law is here for a good reason,” said Professor Juergen Kunze, a geneticist at Berlin’s Charite Hospital.

“Medical research has shown that there is a higher risk of genetic abnormalities when close relatives have a child together. When siblings have children, there is a 50% chance that the child will be disabled,” he said.

The siblings were born into the same family but Patrick was not living with them when his sister was born.

They met for the first time in 2000 shortly before their mother died of a heart attack.

Soon they fell in love and had their first child Eric in 2002. Sarah, Nancy and Sofia were born over the next four years.

A ruling is expected in the next few months.