Shared birthdays

When researching the paternal side of my family, I was intrigued by my great-grandfather, Frank Healy. He was born to Irish Catholic immigrants who settled in Hudson, Columbia County, New York, and the St. Mary’s baptismal record in Hudson identified his birth date as 14 June 1864. This warmed my heart, because I was born 100 years to the month after him. Somehow knowing this made me feel a bit closer to the man my father was named after, but whom neither of us had ever met.

The statistical probability of sharing a birthdate with anyone, even one’s own child, is 1 in 365. These are not bad odds, and certainly significantly better odds than holding a winning Powerball ticket. But what is the likelihood of multiple generations of parents and children, on both the maternal and paternal side, having shared birthdays?

While sharing the same birthday month 100 years apart is a fun coincidence, it’s not particularly impressive. But what is impressive, in a slack-jaw kind of way, is the plethora of shared birthdays that span multiple generations within my family.

On the maternal side of the family, my grandfather was born on June 4, his son Tom was born on June 4, and Tom’s granddaughter was born on June 4. I’m not sure what the statistical probability of this is, but if Tom’s child (not his grandchild) had been born on June 4, the odds would have been 48,000,000 to 1.[1]

What makes these June birthdays even more interesting is that my oldest daughter was born on June 5, … one day before my birthday.

What makes these June birthdays even more interesting is that my oldest daughter was born on June 5, one day after her great-grandfather/great-uncle/second cousin … and one day before my birthday. So now we have consecutive or shared birthdays for four generations and five people of 4–6 June. I’m not a statistician, but I’ve got to believe the odds of this happening are pretty low.

But wait, it gets even better… On the paternal side, my father was born on his father’s birthday; my sister’s daughter was born on her birthday; my brother’s daughter was born on his birthday: if my daughter had been born one day later all three of us would have children who share our birthdays.

It would certainly appear that my family has a genetic memory that predisposes us to having children on or near our own birthdays. It’s fascinating to wonder what sort of memory could be seared into our DNA that would create such a strong propensity. Could the fact that there are shared birthdays on both the maternal AND paternal sides of our family have had something to do with the way my siblings and I share (or nearly share) birthdays with our children?

What’s the statistical probability of so many shared birthdays within multiple generations of the same family? Whatever it is, it’s probably right up there with the odds of winning the Powerball!


[1] “Three generations of same family born on same day: Incredible odds of 48 MILLION TO ONE,” The Express, 15 June 2017.

About Tricia Mitchell

Tricia Healy Mitchell is a genealogist at the New England Historic Genealogical Society and a graduate of the Boston University Certificate program in Genealogical Research. Her areas of experience and research interests include New York, Maine, Massachusetts, and Ireland. She authored the Portable Genealogist: Probate Records and she is a member of the team offering lectures and webinars at the American Ancestors Research Center and at She holds a Bachelor of Science degree in business from the University of Maine.

25 thoughts on “Shared birthdays

  1. My first husband and his brother were both born Wednesday March 8, 5 years apart. And my now husband and his oldest daughter share the same birthday, July 30.

  2. My mother once said there’s a trend in our family of children being born on a grandparent’s birthday. How she thought this I don’t know, because I haven’t found it to be true, although I have to admit, I don’t know some of my cousins’ birthdays. But two years after her death, my grandson — her great-grandson — was born four minutes to midnight, on the date BEFORE her birthday. I chucked and said, well, she was born in a different time zone, which would have made an hour’s difference. So up in heaven, she can be pleased that he was born on her birthday.

  3. Our family has a lot of this. My mother was born on her father’s mother’s fiftieth birthday. I was born on my father’s mother’s fifty-first birthday. Our older son was born on his grandmother’s sister’s birthday. Our younger son was born on his grandfather’s brother’s birthday.

  4. Is there something “romantic” about early September in the family’s traditions? Perhaps the family has always taken vacations on Labor Day weekend?

    The causality is at the conception end, unless there are birthday celebrations involving activities that would trigger contractions.

  5. My half sister and I share our August 1st birthday 21 years apart…and our great grandfather’s youngest sister was also born on August 1st.

  6. There are a number of shared birthdays in my tree. A paternal great-grandfather and his paternal grandmother were born 68 years apart. A paternal great-great grandfather and his maternal grandfather were born 41 years apart. They must have had quite a chuckle over it.

  7. My husband, Andy, was born just minutes before his grandfather’s birthday on the 19th of February. His mother told him she tried to wait for her father’s birthday to deliver but she just couldn’t.
    My husband and I are born one year and a day apart, so the 19th and 21st of February.
    One of our granddaughters was born on our TWEEN day, so the 20th, which is then, her GREAT Great Great Grandfather’s birthday. And another of our grandson’s was born on MY birthday the 21st of February.

  8. My friend has four natural-born children (no c-sections/choosing of dates). My friend’s first was a boy; second was a girl, born on my friend’s very birthday; third was another boy; fourth child was another girl… born on the very same day as the first daughter and their mother. Now, what would be the odds of a mother and both her daughters sharing a birthday? (They might want to buy lottery tickets every birthday!)

  9. I share a birthday with one of my great nieces. No matter what causes it, it is a special bond. We call each other “birthday buddy.”

  10. My brother and I were born on the same date, 4 years apart. We are my parents’ only children. My brother’s daughter married a man with the same birthdate as my brother and I. Her daughter was born on her uncles’s birthday.

  11. I was born on my uncle’s 30th birthday. And my eldest son was born on the 30th birthday of Uncle’s eldest son.

  12. My youngest granddaughter was born on her great-grandmother’s 100th birthday. And great-grandma lived to be 107 so they were able to celebrate several birthdays together.

  13. My dad’s first cousin Dick in California, myself and Daddy’s niece (my first cousin) all shared a birthday. My 13th birthday happened to fall within the dates my parent and I traveled to Calif to visit Dick and family. Double the fun! On a different note, my maternal gf was born on 28 May 1877 and my dad, his son-in-law, died 28 May 1977, which made me also aware of relatives with day-month matching birth-death dates.

  14. I was sure someone would have pointed this out by now, but you can easily google this question about shared birthdays and see the math for yourself. I learned the surprising answer when I took statistics. To have a 50% chance (even odds) of having two people with the same birthday, you need a group of only 23 (or more) people.Not billions! I worked in an office with 150 people; there were six of us with my birthday, January 20!

    1. Count myself and my late twin brother as January 20 babies as well! We do, however also have twin uncles whose birthdays are January 20 and 21 (9 minutes apart) and our grandmother whose birthday is also January 20.

      I switched dates when I procreated and went to the common dates in my husband’s family. He had the same birthday as his father, May 12, and although I was very sure it would never happen because my due date was June 27, sure enough, on May 12, I delivered a small, but gorgeous little girl! To unwittingly continue the tradition, a few years later, my next daughter was delivered 10 weeks early on her paternal grandmother’s birthday (instead of my January 21 due date).

  15. My mother was the youngest of 7. She was born on August 11 as was her next older sister and an older brother who was the first child in the family. So the oldest child and the two youngest shared the same birthday. Ironically, my oldest daughter’s mother-in-law was also born on August 11!

  16. I must be the 1 in 48 million because I’m a female born on my dad’s birthday and my grandfather’s birthday (my mom’s dad). The only thing is that since I was an affair child my mom’s husband at the time was the one who signed my birth certificate, it wasn’t until I was 8 years old that the truth came out about my real father, because my mom and her husband we’re getting a divorce. Her husband knew I wasn’t his the entire time though, since he had a vasectomy and couldn’t have children. Had it not been for that, I’m certain my case would have gotten much publicity. That said there’s no doubt that I’m my fathers child! Imagine being 8 years old and finding out that your real father lived across the street the whole time, needless to say my adopted father absolutely forbid any contact with the neighbors across the street my whole life. They always did leave nice Christmas and birthday gifts on our doorstep though!

  17. My mother was born on her father’s mothers birthday. I was born on my father’s mothers birthday. My oldest son was born on his mother’s mothers sisters birthday. My youngest son was born on his mother’s father’s brothers birthday. How’s that for sharing birthdays?

  18. I share a birthday with my father and grandfather. Against all odds, my youngest daughter was also born on the same day. She is the 4th in a row with the same December birthday. It is a fun bond to share, but causes some confusion in record keeping.

  19. I’m the last of two first cousins in KS and a second cousin in CA, all on my dad’s side, who shared a birthday, so shared birthdays are no biggie. I’m more fascinated by relatives dying on another relative’s birthday. The first example was my dad passing on 28 May 1977, which would’ve been his father-in-law’s 100th birthday. Since then I’ve noticed many birthday-death day “twins”.

  20. I have 3 granddaughters all born on the same day(June 17th) different yrs. to my first 3 children. What are the odds of that happening?

  21. My sisters birthday is the same day as my mother, and mine (son) is the same day as my father. We’ve never come across another family like ours.

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