That was the plot of the Ann Bannon pulp from the early 60's which wasn't reprinted (though I don't remember whether or not they were twins). Paging the Feminist Press at CUNY.......

This story's been running for a week here, but looking through Google News none of the newspapers have anything beyond the guy's original vague anecdote, which in turn was gossip he heard from someone else. Got to be bollocks.

I don't believe it, either.

I remember reading an article a couple of years ago that talked about this kind of phenomenon -- evidently it's quite common for siblings who are separated at infancy and never meet until adulthood that one or both of them will develop a strong sexual attraction for the other. The gist of the article was that there's research going into why this is, if there's some bizarre biological force that's held in check when two siblings grow up knowing each other.

They profiled a few anonymous siblings who went through this (some even briefly gave in to the impulse and had sex), and the common thread to all their stories seemed to be that if they could work their way through the attraction, they could establish a strong, healthy family relationship. Getting there always seemed to necessitate going through tons of pain and awkwardness, though. I think one brother/sister pair even went into therapy to get past it.

Found a Guardian article about it.

The vagueness was due to the fact that they had been guaranteed anonymity by the Court when they applied for an annullment here in the UK.
He mentioned it in the House of Lords as an example of why we need the provisions of the human embryology and Tissues bill.

It is almost certain that they were fraternal twins and as the godmother of 2 fraternal girls they are a physically unalike as chalk from cheese.

I think the story is very credible and once the Judge observed their anonymity in the chat with Lord Alton there is no reason to think anyone is misrepresenting the situation.

There has been work done on consanguinous attraction but it tends to be horizontal rather than vertical I believe. Goggling sibling attraction gives very few links.

There's an AskMe thread going on about this, with a fair number of links (most of which I haven't read yet, but they look interesting!).

Wilder, it doesn't actually say they were granted anonymity. It says "have been kept secret", which appears to be the journalist's way of saying "no one knows" while still appearing to have the facts.

The whole thing seems to be an exercise in building an article out of the very short original quote (last paragraph), giving the impression it's their own story when really they're just rehashing his statements exactly. There's pretty much a 1:1 correlation between the statements in the article and Lord Alton's words.

For what it's worth, the News Of The World quotes a High Court Judge denying all knowledge.

Thanks for the article Stooly. That was a very sad read.
It also happens that there was a dramatic anime made on this subject. Koi Kaze was a very well written serious drama, though watching it will make you more uncomfortable than wearing edible underwear in an ant farm.

I'm all for letting them stay anonymous, but I'm curious as to how they found out they were siblings.

I'm pretty sure they would have to be fraternal twins, unless same-sex marriage has been made legal over there.

That, or a complete fabrication on the part of Lord Alton of Liverpool.

The snopes thread about it is inconclusive. This kind of sums it up for me:

Single-source story...no checkable details...I have no reason to believe it's anything more than Lord Alton's propaganda.

It is almost certain that they were fraternal twins

... Well of course they are, you never get the boy+girl combo when a single egg produces twins! :)