Probability of 4 parents sharing 2 birthdays I'm a math idiot and I'm trying to figure something out. My mother was born on April 10th as was my friend's mother. My father was born on July 4th as was my friend's father.
How do I calculate the probability of that happening?
EDIT: How would one calculate the probability of 2 pairs of shared birthdays? I think this is the answer I'm looking for
Halp.
-Brett

The probability the moms share a birthday is $1/{365}$ (approximately; this ignores leap years). The probability the dads share a birthday is $1/365$.
Since these two events are independent, the probability they both happen is $1/365^2$.
