I’m going to guess that genetics matters, and not the location of gestation. But I’m certain it would have to be debated.
Next question: female monarch uses her own DNA to clone herself. Carries one of her fertilized eggs, delivers her own identical twin.
Does that child become next it line for Queen?
Parliament can tinker with the line of succession to its heart’s content, especially if, in the future, biotech unduly complicates things. Under the current law, though, yes, I think the cloned child would be next in line, assuming the Queen in question had no older children.
What if this happened when Kate was 9 months pregnant and in labor? Would Harry jump right in as king?
“You should have gone with the C-section last week, beyotch!” 
Prince George Alexander Lois Cambridge.
So, under current law, the deciding element is The Royal Vagina, and the first human out of it is next in line?
ETA examples- her own clone, or a surrogate of non-royal lineage or an alien-human hybrid.
Any such change also must be approved by the parliaments of those countries that recognize the English monarch as head of state.
If, let’s say, the Canadian Parliament did not approve the change allowing a female first-born to be monarch ahead of her hypothetical younger brother(s), it would have meant that the hypothetical Princess Noname could have been queen of England but her hypothetical younger brother the king of Canada.
As others have said, no. For the same reason that, if Charles were to die today, Andrew would not become the heir.
No, Harry would still be behind the unborn child, as once the pregnancy was known, as long as a viable foetus existed, it would be presumed to be next in line.
Oh, and Prince George Alexander Louis (not Lois) of Cambridge.
Who enforces all this? If a king simply declares any one of his children or nephews to be successor, won’t his will be respected?
No, no, and hell no. The UK and the Commonwealth are under the rule of law, and the monarch does not unilaterally make law.
The line of sucession is set by a mixture of statute law, mainly the Act of Settlement of 1701, and common law. (Changes are pending in the UK and the Commonwealth realms to amend the line of succession to treat males and females equally.)
The king does not have the power to alter an Act of Parliament or the common law.
It’s good to be the King, but not that good.
I’ve been wondering the same thing. For the first time, two Queens!
No more than if a U.S. President declared anyone his successor.
Can we spin that one another way?
Lets say young prince George turns out to be Gay and enters into a common law marriage with another gay man.
I read somewhere in here that an adopted child can’t inherit (I think), neither of George or partner can give birth (or provide eggs), so the only remaining option to produce an heir would be to use Georges sperm and another woman, whether naturally or artificially impregnated.
Now that would technically mean that the child was illegitimate. Would it be able to be recognised as heir to the throne?
If yes, would some royal status then be conferred automatically on the woman who gave birth to the heir to the throne?