Quote:
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Bookmakers have worked out the odds of three generations of the same family all having boys born on the same day as 272,910 to one.
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For three generations on the same day, ignoring leap years, assuming random birth dates and one child per generation, I figure:
Grandpa born on any day = 1/1 chance, since it sets the day.
Father born on same day = 1/365.
Son also born on same day = another 1/365.
= (1/365)/365
= 1/133,225
If you require that all three are born on a specified date (eg May 8th) it is another 1/365 (for Grandpa to also be born on that date) which works out at 1 / 48,627,125.
I don't think the date can be set in advance, so I go for 1 / 133,225.
However, given that each generation has more than one child, and birth timings are not random, the real odds should be substantially lower. It's very hard to say, but allowing 3 children per generation and some tendency to deliberate seasonal breeding, I'd guess somewhere in the 1 / 30,000 to 50,000 range.
Really there must be scads of them.