It is mainly about morals in the age of contraception. Of course the definition of what incest is is not, which is what you probably meant... Ignore me
By your standards sisters would be okay or an uncle with his nephew. Its totally up to you, if you want to fuck your mother as long as she is postmenopausal?
Idk dude. I'm kinda not with you on this.
Edit: oh wait! If you get a vasectomy/tubes tied, you can fuck the whole family...
Ethan Hawke’s Predestination deals with this, but with time travel instead of cloning. That being said, the incest issue is less about the genetics of it, since its generations over time that becomes the problem (see any royal inbreeding family across time and fiction) vs a one-off situation (for genetics). The bigger issue is the psychological trauma of the abuse of siblings or parents/older relatives.
If we go back to ‘is it or is it not incest’ instead of ‘is incest bad, genetically or psychologically’… I’d say no. Its masturbation. You’re having sex with yourself, and (hopefully) willingly.
There was a episode of Sliders that dealt with that. Quinn almost hooked up with his female self in other world.
So it is possible also there was a movie that dealt with it as well called Predestination with Ethan Hawke that dealt with having sex and making a child with oneself. So sci fi has done it.
My point is - we know that cloning is real and possible today.
Is changing gender also (soon to be) possible, or is that something that will remain exclusive to scifi for forseeable future? I have not a slightest idea.
No one doubts that anything is possible in scifi movies, that is why there is that word fiction.
So your second point should be phrased "Is changing sex also (soon to be) possible", as sex is genetic and gender is a concept.
Maybe with some radical gene therapy sex could be changed, but I imagine that to be a rather long and unpleasant process if physical changes happened. It would probably be more feasible to make a clone with the different sex and then transplant consciousness. That just raises further questions like if you died and is that still you. Probably before that is viable we will be uploaded to computer systems to escape the environmental effects of our actions and your avatar will be up to your whims.
Heinlein's "all you zombies" is an early version of this.
In terms of biology, it's extremely rare for humans to have fully functioning sets of both reproductive systems. The reproductive physiology develops from the same parts so it either develops "male", "female", or (more common than people think) somewhere in between but not "both". A clone may or may not even develop in the same way.
One other possibility, though also very rare. is near-identical twins. If twins have the same genetics (in other words, they're identical twins) but have intersex conditions that result in different reproductive development it's conceivable that they could reproduce with each other. It's uncommon to be fertile incongruous with your genetics, though, so again: this would be extremely unlikely.
That said, in a sci-fi context there are some options. Biological hermaphroditism is possible in animals, though there aren't any vertebrates on Earth, so conceivably an alien species could encounter this problem.
Advanced medicine could also build people a new reproductive system and implant it, giving them the counterpart they lacked.
Of course, in that case, advanced medicine may also be able to give you someone else's reproductive genetics (ex, implanted sperm or eggs) and thus effectively sidestep the genetic problems. I'm imagining a particularly narcissistic person getting a gender-flipped clone of themself and using someone else's genetic material to have a kid with themself but also avoid the shallow gene pool problem.
Of course, you don't need to go that far. If you're female (or have those parts anyway) you can just do IVF. Don't even need to clone yourself, then.
One other possibility, though also very rare. is near-identical twins. If twins have the same genetics (in other words, they’re identical twins) but have intersex conditions that result in different reproductive development it’s conceivable that they could reproduce with each other.
Yeah, aren't there occasional cases of have XY (male) and X0 (female, Turner's syndrome) twins? That seems like the closest to OP's scenario, and yes, it would definitely be incest, of pretty much the highest possible degree.