Assume that births are uniformly distributed across the 12 months of the year. If the first person selected was born in month m, the probability that the second person selected was born in month m must be 1/12.
The probability of selecting 2 people at random who were born in the same month is 1/12. I am hoping that this answer has satisfied your query and it will be able to help you in your endeavor, and if you would like, feel free to ask another question.
