Closest to My Birthday – 52 Ancestors # 37

I grew up with a mother whose birthday was the day before mine.  It was always just one of those things, and in a family of 5 children very close in age one of the things that made me feel a little different.  In terms of close relations, my mother’s birthday is the closest to my birthday.  However, when this theme came up, I already knew that I had at least one ancestor not so close whose birthday was the same day as mine since I had noticed it in my database.  I thought I would look to see if there were any others, just to know this factoid.  I figured out how to get my database to filter all the people by that date, and discovered that there are actually 6 people with the same month and date of birth as mine.  None in the same year though.

Next I figured out the relationship with me for each of these ancestors.  It ranges from second cousin once removed (the closest) to a first cousin 5 times removed.  There are also a couple of third cousins at one or two removes.  The second cousin once removed was also closest in terms of the year he was born, being only sixteen years older.

The birthday problem or birthday paradox is a standard problem in probability theory.  You may have heard that in a room with 23 people the likelihood of two people sharing the same birthday is about 50%.  This assumes some things the people in the room were randomly chosen, like birthdays falling equally on any given day, and does not take leap years into account (the individuals born on February 29).  For the question of likelihood that someone else’s birthday falls on my birthday, the odds are different.  My birthday specifies a month and date.  This changes the formula.  For a greater than 50% chance that one person in a roomful of people has the same birthday as you, there would need to be at least 253 people.  This article explains more than I wanted to know about the question.  Since my genealogy database currently has 3231 people in it, it makes some sense that there should be at least a couple who share the same date of birth as mine.  Not everyone in my database has a birth date entered, some have nothing and some have a partial entry (year, approximate year, sometimes a month as well without a date).  So the pool of people I can compare to is smaller than the total.

Knowing that I have 5 matches, I was curious about my siblings so I ran the same sort for each of them.  We were all born in different months.  My sister, born in February, had 8 exact matches.  My brother born in March had 4, my brother born in November had 6 and my brother born in October had 3.  I don’t know what this means in any statistical way – likely nothing – but I think it is interesting.