Birthdays

When I was in hospital having our son M - on October 17th 1981 - our next door neighbour at the time - Nita- was in hospital having her son, he arrived a few hours earlier than M so had a birthday on the 16th.
 Our neighbour's eldest son was born in 1980 on April 16th, my birthday. Nita herself had her birthday on November 4th  and in 1987 our youngest daughter was born on............ yes you guessed - November 4th. Which is also Col's sisters birthday.
We have friends in Essex. He has his birthday on April 15th - the day before mine and  she has her birthday on November 1st, which is also the date of Col's brothers birthday.
Confused?
I once heard this question years ago on a Radio 4 Numbers programme - " how many people - made up of your family and friends -  do you have to have in a room to have two people with the same birthday? You would think it would be 366, but they said it's only 16.
It's certainly right with our friends and family, but is it just coincidence?
I really need to know!

And a PS -  Happy Birthday son, poor old fella is 34 today.

Back soon
Sue