Originally Posted by who

But hang on a minute, incest is illegal, isn't it? But using terms such as 'twins' and 'sisters' in conjunction with a porn site is surely the same as using the illegality of it to promote it.?.

So what you're doing is saying "Here's something illegal for you to enjoy!"
(Although the girls 'don't touch' and the actual content is legal)

Now, I don't have any personal feelings towards the actual content one way or another, but, this equates to saying "Look, we have 15 year old models!"
(even though they're actually 18 and the content is legal).

Essentially, it's promoting incest.