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.
markj-ga |
