A possibly Varley short fiction about a clone, his sister-progenitor and a complicated family history

Question

I read this short story (or perhaps novelette) at least 40 years ago, in a collection. I realise now that the story might well be by John Varley. But I'm pretty sure it was not a pure Varley collection. It's only after I asked here this question that I started to associate frequent sex changes to Varley's "Eight Worlds" books, but there are so many of them...

So a young man (IIRC, XY genotype, but he had already been female, and has changed back) who lives with his mother knows he is a clone. For the first time his progenitor (of course the same genotype, but presently his older sister) comes to visit them on that planet, from the one from which his mother and himself came, and where she lived with one of their mother's friends. He knows there is something really bizarre in his family. Why did his mother leave her child with a friend, and move to another planet with a clone? But neither his mother nor his sister-progenitor would tell him the "big secret".

At some point clone-brother and progenitor-sister find themselves in a life-threatening situation. In these dire straits, the sister tells him all.

The woman she was living with is really their common mother. The supposed "mother" of the young man is in fact their common father.

They survive but I don't remember the details of the end of the story.

Answer 1

I believe you are looking for "Retrograde Summer", indeed part of The Ophiuchi Hotline by Varley, the same as The Phantom of Kansas. The siblings get trapped underground on Mercury, and wind up discussing their progenitors and clone nature.

This review goes into a bit more detail.

Timothy is a 17-year-old aspiring pilot on Mercury, living with his mom Dorothy, has a special visitor coming in from Earth’s moon: Jubilant, his sister, whom he has never met before. Jubilant is older “by three E-years,” making her the big sister, and the two don’t exactly get along at first sight. This is all a bit of an odd experience since Timothy isn’t sure how Jubilant is his sister, and as we learn about family arrangements for this future humanity it’s hard to blame his confusion.

....

Thus other means of generating tension are required, and in the case of this story there’s already enough tension between the family members, since Timothy gets the strong impression that Dorothy is keeping secrets from him as to his exact relationship with his sister. It’s hard to blame him, considering Timothy and Jubilant turn out to be a bit more related than the former had previously thought.

....

So what counts as religious insanity in the context of the Eight Worlds? As Jubilant tells us, after she and Timothy inevitably get trapped in an earthquake, Dorothy used to be “genotypically” a man… and also their dad. The thing about families in Eight Worlds societies is that they don’t exist anymore, or at least the nuclear family model is considered taboo. It’s one child per parent, and the idea is that each parent would raise their child more or less by themself. You might have a mother, but you wouldn’t have a “father.” That Dorothy used to be a man but also used to be the “father” in a couple that practiced the fringe religious belief of raising children together as a couple (gasp) comes as a shock to Timothy. Oh, and there’s another thing: Timothy is a clone. Jubilant was born first, and in fact Timothy was a clone grown from Jubilant while the latter was still a toddler; so the reason the two look so similar when both are women is that they’re genetically the same person. After finding this out Timothy says it’s a shame the two can’t have sex together while trapped under the rubble, and I can’t tell if this is meant to be a joke on either of their parts. After finding out they’re not siblings (at least not in the traditional sense) there’s some romantic/sexual tension, but it does unresolved. Does fucking your clone count as incest? Mind you that Varley would write clones boinking each other in some later Eight Worlds stories with the appropriate amount of gusto. Incest enjoyers will get a bit of a kick out of the sexual tension here. Anyway, Timothy and Jubilant are old enough and close enough in age that it wouldn’t really be a problem, at least compared to some of the more questionable relationships in Varley’s fiction (Heinlein has a lot to answer for).