# Two consanguineous human princes (same father and mother). How far apart in age could they be? [closed]

In a prosperous human kingdom of the near future, there are two princes, their ages alone could set them as father and son.

This kingdom bans genetic modifications, and also the freezing of reproductive cells and/or embryos.

Both princes were conceived through natural means, born of the same father and mother.

The king and the queen were married at their earliest ages for political reasons, but both are blessed with peak vitality and health. Never has anyone heard of one of them even afflicted by the common cold.

Historians, biologists and physicians all say that there were no way the two princes' ages could be further apart.

What is the maximum age gap possible between the princes?

• Is this a real question or a riddle? Commented Mar 15, 2015 at 20:34
• If it is meant as a riddle rather than a real question, I think it belongs on Puzzling.SE Commented Mar 15, 2015 at 21:42
• It differs in the acceptable answers. For a worldbuilding question, any answer that gives information about what was asked is a valid answer. For a riddle, there's only one correct answer, and all other answers are wrong. Commented Mar 15, 2015 at 22:00
• There's no possible way to give an exact answer, as it depends on individual variations. Commented Mar 15, 2015 at 23:44
• @celtschk actually several riddles have more than one solution. Many are not meant to, but do anyway. When people insist that even these have only one solution they aren't asking a riddle. They're playing, "guess what I'm thinking". Commented Mar 16, 2015 at 2:46

A woman can get pregnant approximately between 15 and 50, so the maximal age difference between two sons of the same mother is about 35 years. Certainly large enough that one could be the father of the other.

Note that those ages can vary for different women, but even between 18 and 40 are 22 years, so even assuming a very late puberty and a very early climacteric period you'd get enough age difference.

• Sorry but you did not answer the question. I asked "The maximum age gap possible. Not an estimate. Commented Mar 15, 2015 at 21:38
• I answered it as a worldbuilding question, because that's what this site is about. In the mean time, you revealed in comments that you meant it as a riddle, for which this is IMHO the wrong site (and there's a Stack Exchange site where riddles are on-topic, Puzzling.SE). Commented Mar 15, 2015 at 21:43

According to wikipedia, the earliest recorded motherhood for healthy woman is at age 8. There are three registered cases of motherhood at ages 5 and 6, but in all the cases the girls had an hormonal defect. Since the queen is healthy by all standards, so hormonal defects are ruled out. Medicine defines precocious puberty if it is onset before age 8, and since the queen is healthy, she entered puberty at age 8.

The eldest prince was born when the queen was age 8.

Also according to wikipedia, the oldest natural conception birth mother was age 57. Due to concerns regarding accuracy of early XX century birth records and age count, lets take into account only births that occurred in the XXI century.

The oldest prince then was born with the queen age 57.

Since the age gap could not be bigger by the opinion of the specialists cited, the age gap then is 49 years (assuming the youngest prince birth month after the oldest prince, in the calendar).

Regarding the queen's health, and the relationship between the age of the menarche (first period) and menopause:

There is conflicting evidence concerning the relationship between ages at menarche and menopause. Some studies have found a relationship between earlier menarche and earlier natural menopause or perimenopause,[92,94,126,127] a few have reported a relationship between earlier menarche and later menopause,[128,129] but most others have found no association.[69,130-133]

Since there is no scientific consensus, the reader is free to conduct an impact evaluation on the papers linked in that article, to see where the reader feels more comfortable with.

• However you didn't give any evidence that the same person that has such an early puberty can also have such a late climacteric period. So when being pedantic (as you were on my answer), you also didn't answer the question. Commented Mar 15, 2015 at 22:08
• @celtschk can we just shrug it off as the adaptation period on the first post by a new user? I can mark your answer as accepted (as I avoid accepting my own answer on other SE sites). But can we let this issue die? I promise to be a good boy in future questions. Or do you want me to leave the site? Commented Mar 15, 2015 at 22:13
• Well, just for the record: The one upvote you currently have on your answer (and already had before your comment) is mine. So it's not that I consider your answer a bad one. Anyway, thanks for the accept. Commented Mar 15, 2015 at 22:17
• Why did you ask the question if you were going to answer it yourself? Commented Mar 16, 2015 at 0:22
• The problem I have with this answer is that even from a pedantic point of view there's no reason this is correct. The fact that the oldest natural conception was at 57 doesn't mean at all that there is "no way the two princes' ages could be further apart" because there's no evidence that this exact age is the maximum limit. There's no good reason the queen couldn't become pregnant at an even later age. Yes, it's highly unlikely, but it's preposterous to say it would be impossible just because there is no precedent, and no biologist or physician with a bit of common sense would assert this.
– zeta
Commented Mar 16, 2015 at 9:20