The probability of any any one person having any one birth month is 1/12; or one out of 12
the probability of any two people having the same birth is only 1/12*1/12 =1 /144 so the probability that two people will share the same birth month is only one out of 144.
However, and here is the reason why it is stupid to think that playing the lottery by more tickets increases the your chances of winning, YOU ARE NEVER CERTAIN.
Let me give you a simple example:
If you flip a coin, the probability of getting heads or tails is always 1/2. But there is no certainty, no matter how many times you flip the coin. If you flip the coin 100 times you should get heads or tails about 50 times, but there is no guarantee.
I hope this helps.
Apr 9th, 2015
Sorry for the bad grammar, I hope you are able to see through it.