Overpopulation is when when a city, town or even whole country's population is so dense. That the condition of living is greatly decreased. The amount of people exceeds the amount of resources.
Lack of individuality, because everyone's birthday is compressed into two months you probably would have to share your birthday with 10 or 15 other people you know.
Lack of freedom to see your brothers and sisters. Ignorance of what the other gender is like.