Originally Posted by Tanky:
“It's wrong because it's a taboo. People of the same blood relation who are first family relatives, are not meant to do this. Some things are just wrong, there's no further explanation needed.”
It's a very sensible taboo that arose a long time ago when it was seen that children born to a brother and sister often had disabilities. But that doesn't apply to same sex siblings.
Anyway I'm going to shut up, as I'm probably coming across as creepy to a lot of people