Incest between siblings appears to be very rare in Western societies according to the available data but those affected describe how difficult their situation is in light of the threat of punishment. They feel their fundamental freedoms have been violated and are forced into secrecy or to deny their love. The majority of the German Ethics Council is of the opinion that it is not appropriate for a criminal law to preserve a social taboo. In the case of consensual incest among adult siblings, neither the fear of negative consequences for the family, nor the possibility of the birth of children from such incestuous relationships can justify a criminal prohibition. The fundamental right of adult siblings to sexual self-determination has more weight in such cases than the abstract protection of the family.
So incest is now considered to be a "fundamental freedom" - the language of freedom is being invoked once again. And what is meant by freedom? It is the "fundamental right" to "self-determination" - and it is this right to self-determination which is thought to trump all other considerations, such as negative consequences for the family or the problems that arise for the children born to such relationships.
Here again we have a problem doing great harm to Western societies. Freedom is held to be the sole, overriding good and freedom is understood in a limited way as individual autonomy. Other goods in society are sacrificed to this one reductive understanding of morality - which means inevitably that people don't even end up feeling free or autonomous.
The better option is for a community of people to try to get as close as possible to an understanding of an "order of being" - in which a range of goods are harmonised as far as possible. That is not only the best way to uphold more than one good, it's also the best way to maximise freedom and to make freedom meaningful. (Is it really a meaningful understanding of freedom when incest starts to be considered a "fundamental freedom"? What's next?)