# What is the relationship between the man and the woman?

A man walks up to a house and knocks on the door.
He hears a woman asking: "Who is it?"
The man answers: "My mother-in-law and your mother-in-law are mother and daughter"

What is the relationship between the man and the woman?

• "A riddle gives indirect clues about an unnamed object or concept to be identified. It is often presented in the form of a poem." I still don't think that applies to this question... – Wu33o Aug 4 '16 at 9:10
• @Wu33o The riddle tag is often misapplied. Just edit it out :-) – Rand al'Thor Apr 13 '20 at 9:18

The man can be the girl's father-in-law.

But:

The man can also be the girl's mother-in-law's brother-in-law. (try saying this 3 times out loud)

Let's make this notations:

M - the man
G - the girl
MML - man's mother-in-law
GML - girl's mother-in-law.

We get this:


MML
/\
mother- daughter/  \ mother-in-law - son-in-law
/    \
GML     M
|
Mother-IL-Daugher-IL
|
G


From this tree we can deduce that

M is the husband of GML hence his is the girl's father-in-law.
Or GML has a sister or brother and M is married to that brother or sister.

Man is father-in-Law of the girl

If Daughter's mother-in-law is man's wife, so that man's mother-in-law is his wife's Mother. So in relation Man is father-in-law of the girl.

The woman could also be

The man's mother-in-law, because she is married to his spouse's mother

• Ah, the 21st century, politically correct answer. – Peregrine Rook Aug 5 '16 at 9:34

The key statement is, “My mother-in-law and your mother-in-law are mother and daughter.”  Note that this statement omits the critical word, respectively, so the order of the two lists is not necessarily the same.  The accepted answer assumes that the mother-in-law of the man (who knocked) is the mother of the mother-in-law of the girl/woman/female who was inside the house.  But it’s possible, as in Dane Andersen’s answer, that the mother-in-law of the man (who knocked) is the daughter of the mother-in-law of the girl/woman/female who was inside the house.  This leads us to the following family tree (where “=” represents marriage, and “/”, “|” and “\” represent parent-child relationships).  Let M0 and F0 represent the man and the female who speak in the riddle (respectively).

       F3
/ \
F2  M4 = F0
|
M0 = F1

i.e., the man could be

the son-in-law of the woman’s sister-in-law.

The widower married a woman whose widowed mother married the widower's son.

I see other answers are very intricate, but in the fact the answer is simple:

If I use this notations:

M - the man G - the girl

G is M Aunt.
I mean G is M.Mother sister.

So

G.mother and M.mother are mother and daughter.

I'm confused with accepted answer really !

• I think this would only be possible if the man and the woman (his aunt) were married. – Schorsch Aug 4 '16 at 14:04
• You've completely ignored the mother-in-law relationships. – Matthew Read Aug 4 '16 at 16:29
• True answer is clear for me, because this is an old and public Persian mystery. however maybe here people think the answer must be intricate. – Milad Abooali Aug 4 '16 at 20:27