Propositiones ad Acuendos Juvenes/Problems/11 - De Duobus Hominibus Singulas Sorores Accipientibus

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Propositiones ad Acuendos Juvenes by Alcuin of York: Problem $11$

De Duobus Hominibus Singulas Sorores Accipientibus
Two men marrying each other's sister
If two men take the other's sister in marriage,
what is the relationship between their sons?


Variant 1

De Duobus Hominibus Singulas Matres Accipientibus
Two men marrying each other's mother
If two men take the other's mother in marriage,
what is the relationship between their sons?


Variant 2

De Patre et Filio et Vidua Eiusque Filia
A father and son and a widow and her daughter
If a relict or widow and her daughter take a father and son in marriage,
so that the son marries the mother and the father marries the daughter,
what is the relationship of their sons?


Solution

Cousins, twice over.

$(1): \quad$ The sister of the father is the aunt, who is the mother of the cousin

and:

$(2): \quad$ The brother of the mother is the uncle, who is the father of the cousin.


Historical Note

According to David Singmaster, this problem, along with two related problems (no pun intended) originating from Bede which he also documents, are the earliest of the strange family type.


There are contemporary examples of such:

At 52, Rolling Stones bassist Bill Wyman married 18-year-old Mandy Smith but divorced after a year.
Bill's 30-year-old son then, Stephen married Mandy's mother, age 46.
Therefore, Bill became the father-in-law of his ex mother-in-law
as well as the stepgrandfather of his former wife.


Sources

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