[Jack_]

Now you see...as disgusting as this may be, and something I wouldn't even want to think about participating in, if these people are content and happy doing this...then so be it, it's their lives, and...well, yeah, it's their sex lives.

The only time it becomes a problem is if they attempt to have children, as then there could be detrimental effects on the child, which is unfair. Aside from that...if that's what they want to do, then that's that, really.