Genetics and health issues aren’t a big topic now, because of disabilities caused by genes. If your jurisdiction allows for example people with down syndrome to reproduce, you can’t argue about genetic defects by incest, as they are less likely/server. Here politicians did switch their argumentation towards protecting the family, which makes sense but only when they grew up as family. The problem is when siblings didn’t know each other, when they grew up, later fell in love and only then find out they are blood relatives, they legally can’t reproduce. You can’t argue with protecting the family, because they never where family. They don’t see them as brother and sister.

In Germany there is a group who is fighting to legalize it. About consenting, there is a different law in Germany, which protects that. In Germany for the age of consent, we have 3 categories (14, 16 and 18). The one that matters in this context is everything under 18. If one partner is under 18, you can’t fuck them, if you have a specific relation like teacher, family member, guardian. Also this only applies to consent. Rape is still rape.

But to be fair, a lot changed recently and being against incest “just recently” (still over 10 years) weakened their arguments. They don’t reevaluate everything that gets affected by court decisions or law changes, if now something else got weakened in their arguments. Consenting incest not between guardians, aren’t that many. It needs a group to collect facts and arguments and then need to present them but that doesn’t even guarantee politicians to act