They should be allowed to reproduce... since we can't force people to not reproduce, they should have that right, especially if they understand the problems that arise from incestuous babies and are willing to risk it. I think that answers question 2 since a government shouldn't have any power to affect our reproduction.
No because it is discriminatory against gender (and sexual orientation) but disallowing both is not a logically valid solution since there is no reason to dis-allow gay sibling marriage, except that it allows for same sex sibilings to get married and the consequence behind that is bad (which I disagree with... I think it's a good thing... more rights for the individuals).
I mean saying that you shouldn't reproduce because it could lead to genetic defects is like saying people with genetic defects are somehow inferior and have less rights compaired to those without genetic defects.
You see my mind keeps switching to the perspective of a governing body. On a purely philosophical basis, I can agree with you mostly. But in this thread at least I have primarily been arguing from the position of a governing entity. Ie/ If I had control to change society, which direction would I take it?
And as a governing entity, I'd definitely place a restriction on the legality of incestuous marriage. To add to my earlier reasoning (the influence on cultural attitudes, social norms) is that unlike homosexuality, I think that our desire/lack of with sibling relationships is mostly cultural. We are grossed out by it because we're taught to be. In other cultures there actually were sibling marriages and that was normal. Especially in our globalised society with our speedy communication methods and the reduction or time and space through technology, the allowance of marriage between siblings
could result in a huge cultural change where being incestuous becomes a normal part of life.
So from that perspective of a governing entity, I'd probably not want to run the risk of this happening. You'd then likely be running a nation full of disabled people who can't work or function normally, your economy would die and it would be a complete wreck.
I'm one of those people who always thinks of the consequences before doing anything