[Inziladun]

Originally Posted by Eorl of Rohan

I mean, brother marries sister in lots of cultures (especially in royal families, to keep the bloodline pure).

Originally Posted by Eorl of Rohan

Even if she did, nowhere on Silmarillion does Eru or the Valar state: "thou shalt not marry thine own brethren".

Yes, royalty in the 'real world' often married their close kin, but at least in Europe, that was mainly a result of their practice of arranging marriages between their offspring and that of other thrones, in order to increase their influence. Over time that led to a lot of shared genetics in royal houses. However, I don't think they commonly consorted with such close kin as brothers and sisters.

In Tolkien's world, such intermarriage seems to be strictly taboo, even without an 'official' decree from the Valar. We see it in the Eldar, with Maeglin:

....he loved the beauty of Idril and desired her, without hope. The Eldar wedded not with kin so near, nor ever before had any desired to do so.

The Silmarillion Of Maeglin

And the Dúnedain in Númenor, who took many of their laws and customs from the Elves:

But Pharazôn took [Míriel] to wife against her will, doing evil in this and evil also in that the laws of Númenor did not permit the marriage, even in the royal house, of those more nearly akin than cousins in the second degree.

The Silmarillion Akallabêth

So there are two examples of close marriages being disallowed, and both those instances merely regard first cousins.

Incest between immediate family would have been an even greater horror to those in Middle-earth, at least those of the 'enlightened', in the west.

It seems clear that it wasn't the thought of Túrin being dead that drove Níniel to madness, but the knowledge the she was carrying his child.

Originally Posted by Eorl of Rohan

Why would it be a sin? It would be weird, but not Oedipal marry-your-mother weird. Besides, isn't suicide/infanticide sinful as well?

I don't claim to be an expert on the matter in the real world, but generally the taboo would stem from the knowledge that the genetic mixing would result in birth defects and unhealthy descendants. I don't see why that would be different in ME.

Originally Posted by Eorl of Rohan

Don't you think Niniel and Turin might have worked out a viable solution other than double-suicide to this tangled web of deceit,
if Niniel realized in time that Turin was unconscious but still alive? Somehow overcome this, together?

I don't think either could have dealt with the horror they felt. Think of Níniel's words:

O happy to be dead!

She wasn't mourning Túrin; she envied him, that his anguish had ended.

Originally Posted by Eorl of Rohan

I know that I'm a sucker for happy endings, but I cannot help but wonder whether Niniel would've killed herself she knew Turin lived.
I understand her jumping off a cliff in her despair at her husband's death and the shock of what she found out,
But what would Niniel and Turin have done if Niniel knew Turin was alive? (I assume filing for divorce wasn't an option, but still.)
.

I think she would have done the same, if Túrin himself had tried to stay her. The thought of carrying the child to term would have been unbearable to her, and suicide the only option. She's really the one I have the most pity for in the whole sorry tale, not Túrin.