Math Is Fun Forum

I have recently discovered that a married couple I am friends with have the same birthdays (same day/month - different years) as my mother and father.   My mother and the other woman share July 26, and my father and the man share April 20th.   

Can anyone tell me what the chances of this occurance are?  We are having a bit of a disagreement over whether it is 365 cubed or 365 squared.     

Also, are there any other facts that matter?  We all lived on the same street, etc?   

Please, I am no math genious here.... I need expert help!