I have been reading about the birthday paradox & was trying to take it further & apply it to an example from my own life:-
I am a Brit married to an American. My British sister-in-law shares the same birthday, 19th January, as an American friend that I know through my husband. Both of them gave birth to a son on the same day, 26th June 2011.
I couldn't even get past the probabilities of just knowing two people sharing birthdays whose sons were born on the same day, let alone including the two continents! Anyone fancy having a stab at it?
EDITED.... OK - clarification asked for.
1) What is the probability of knowing two people who share a birthday and who also have a child born on the same day. 2) Whether/How that probability is affected by the fact that number of American friends of my husband that I know directly is about 12. 3) Whether/How that probability is affected by the specific month/day of birth. 4) Whether/How that probability is affected by the two people being in different countries/continents (UK & USA).