Well, I might find it icky, but it doesn't mean it's wrong or moreover, should be illegal.
With siblings, (and cousins too I guess. Here in Finland cousins can get married, but it's frowned upon) as long as they are adults, why not. But with parents/aunts/uncles, and the kids, no. Because the older person would be in a position where they have the power over the kid, and can take advantage of it.
As for children, are there any countries that make it illegal to have kids with close relatives? Actually, I suppose there are(or have been, for example US had all kinds of wacky laws about what kind of sex is lawful), but would it be enforced? Unless it's one of those countries that beheads women who get pregnant outside of marriage or something.
And well, the issue here is, to what extent the people should be able to choose who they have kids with. And it's tricky, but I don't think the goverment has the right to tell people they can't.
ciortas1 said:
It is, after all, both useless in a biological sense and, I think, on the point of lesbians is also unnatural no matter which way you slice it (because from the male side it can be argued that it occurs in nature therefore is natural)[footnote]Or I'm ignorant[/footnote].
I'm not making any argument about this(and the whole "natural" argument won't get us anywhere anyways), but lesbianism occurs in other animals as well. Some deer do it quite a bit, and monkeys, at least.
Biologically speaking, gay couples will still take part in taking care of the children, even if they would be those of the near relatives, thus indirectly helping related genes to survive.
The same could be said about incestuous relationships as well, but there is the risk of inbreeding. But to what extent should the people have the right to choose their mate is the ethical question here.