When Queen Elizabeth II became Queen on the death of her father, she was only able to do so because she had no brothers. (Otherwise, her eldest brother would have become King, under rules still in place today.)

What if, on that event, her mother happened to be pregnant with a boy? Would that boy be the King?

Possible follow-up question: What if the pregnancy is so new that the gender is unknown?

(I'm specifically interested in what happens under today's laws. I'm using Elizabeth II as an illustrative example. I don't think the laws have changed since then but I'm clarifying here in case they have.)

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    "I don't think the laws have changed"...except that they have changed. Nowadays, in the UK (and Commonwealth Realms), the eldest child becomes monarch, regardless of gender. Commented Jun 30, 2014 at 19:31
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    Traditionally the daughter would have the wife of the king killed so that her brother could not challenge her claim to the throne. Commented Jul 1, 2014 at 15:18
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    @Chad: that's not true; the current Queen's mother had the title Queen, and she was not of royal blood either. Specifically, "All female consorts have had the right to be and have been styled as queens consort". Commented Jul 2, 2014 at 16:12
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    Interestingly a somewhat simliar case is regulated in german inheritance law: You have to be alive to be able to inherit - and those who are already sired are considered to be alive before the case of succession. Commented Jul 2, 2014 at 23:36
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    @TomAu The question can easily be extended to monarchies with “fully cognate succession”. What if the queen is pregnant with her first child? Could one of the king's younger siblings or their issue succeed him or do they have to yield to the unborn child?
    – Relaxed
    Commented Nov 3, 2014 at 8:57

2 Answers 2


As multiple comments have mentioned, the laws governing succession in the Commonwealth are currently changing from male-preference primogeniture to absolute primogeniture.

In either case, though, a foetus not yet born has no rights under the law of the UK, and as such would have no claim to the throne, as it would have no claim to inheritance from its father's estate on his death.

Thus, if a monarch died under male-preference primogeniture the eldest living son at the time of death would become the new monarch; for lack of sons, the eldest daughter.

Expanding to absolute primogeniture, on the death of a monarch with no living descendants but with a pregnant queen-consort, he would be succeeded by his eldest sibling (or their descendants) as he has no living descendants in the eyes of the law.

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    (+1) Interestingly, France does not have this problem anymore but in civil matters, it still applies the Infans conceptur pro nato principle. It seems the tradition in the UK is quite different.
    – Relaxed
    Commented Feb 6, 2015 at 13:49
  • @Relaxed France is a Civil Law country, not a Common Law country.
    – nick012000
    Commented Aug 31, 2020 at 0:56
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    @nick012000 Yes, obviously but I guess I still thought it was interesting to note the difference as I wouldn't necessarily expect that to matter directly to something like the succession of of monarch. Civil codes, etc. developed much later.
    – Relaxed
    Commented Aug 31, 2020 at 5:35
  • I'm not clear on British rules but Alfonso XIII became King of Spain despite being born after his father's death - his mother served as regent. (The only posthumous births in England/UK to take to the throne did it at the head of armies and a long time ago: Henry VII and William III.)
    – Stuart F
    Commented Sep 16, 2022 at 13:20

As the law is now, an elder daughter takes precedence over a younger son, so there is no way way for an unborn child to acquire the throne in preference over someone already born.

However, Parliament has the freedom to vary this. The Regency Act 1830 was introduced to cater for possible problems in the succession after the death of William IV. His heir presumptive was Princess Victoria of Kent, who became Queen Victoria when William died in 1837, Victoria having reached 18 and thus not requiring a regent.

The act specifically provided that if William's wife, Queen Adelaide, was pregnant at the time of William's death, that child would succeed to the throne on birth. If the child had died as an infant, Victoria would presumably have succeeded to the throne a second time. Fortunately, none of these things happened.

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