Google Answers Logo
View Question
Q: Siblings Birthday ( No Answer,   3 Comments )
Subject: Siblings Birthday
Category: Family and Home > Families
Asked by: spring0724-ga
List Price: $2.00
Posted: 23 Jul 2004 11:25 PDT
Expires: 22 Aug 2004 11:25 PDT
Question ID: 378215
what are the statistics  for siblings born on the same day, three years apart?
There is no answer at this time.

Subject: Re: Siblings Birthday
From: markj-ga on 23 Jul 2004 12:10 PDT
I doubt if such statistics has been compiled.  And, if you are asking,
"What are the chances?"  I think that more information is needed.

In the simplest case, it seems to me the answer would be approximately
a 1/365 chance that two siblings born three calendar years apart would
have the same birthday.  I say "approximately" because about one out
of 1096 children born in any contiguous three-year period are born on
February 29 of a leap year, so their chance of having the same
birthday as a sibling born in that three-year period is zero.

This simplest case assumes that the universe of people we are
considering is composed of every person who has one (and only one)
sibling who was born in the calendar year occurring three years before
or after the one in which he was born.

If you change those facts (more qualified siblings, e.g.) the answer
would be different.  And, of course, if you want to know the odds that
any random person you meet on the street has a sibling with the same
birthday three years before or after him, you would have to supply a
whole lot more information.

Subject: Re: Siblings Birthday
From: nfpolaris-ga on 23 Jul 2004 14:55 PDT
comment: in my family, my brother, cousin and grandmother are all born
on the same day...what are the odds?
Subject: Re: Siblings Birthday
From: setzer-ga on 28 Jul 2004 13:57 PDT
in my family, my sister, cousin, and uncle all have the same birthday!

Important Disclaimer: Answers and comments provided on Google Answers are general information, and are not intended to substitute for informed professional medical, psychiatric, psychological, tax, legal, investment, accounting, or other professional advice. Google does not endorse, and expressly disclaims liability for any product, manufacturer, distributor, service or service provider mentioned or any opinion expressed in answers or comments. Please read carefully the Google Answers Terms of Service.

If you feel that you have found inappropriate content, please let us know by emailing us at with the question ID listed above. Thank you.
Search Google Answers for
Google Answers  

Google Home - Answers FAQ - Terms of Service - Privacy Policy