The government advisory body had been considering the question following a 2012 case at the European Court of Human Rights (ECHR) brought by a man, Patrick S. in an incestuous relationship with his sister, Susan K.
He argued that the law against incest was unconstitutional, but the German Constitutional Court found against him in 2008. The ECHR also rejected his case.
The Leipzig couple were in a relationship and had four children, two of whom were disabled. Patrick served more than three years in prison after criminal proceedings were brought against him.
Now a majority of the Ethics Council's 26 members, who are drawn from prominent scientists, doctors, theologians and lawyers, has recommended that politicians reconsider the law.
'Basic rights denied'
“According to all available data, sibling incest appears to be very rare in Western societies,” the government-funded advisory board said in a statement.
“But affected people have described how difficult their situation is,” the statement continued. “They feel that their basic rights are not respected and forced into secrecy or denial of their love.”
The Ethics Council argued that the criminal law was not the right way to uphold social taboos or set up boundaries for people's sexual behaviour.
They also ruled out the potential consequences for the family or the possibility of the couple's having children as grounds for incest to remain a crime.
“The right of adult siblings to sexual self-determination weighs heavier in these cases than the abstract good of the family,” the Council said.
Nine members of the Council objected to the motion, saying that the law “protected the integrity and incompatibility of different familial roles, as an important precondition of healthy personality development.”
They argued that unlucky rare cases, such as half-siblings meeting one another later in life and beginning a sexual relationship, could be dealt with by guidance to prosecutors rather than a change in the law.
The council has previously ruled on dementia and genetic diagnosis.