[TomCollins]

There is one extremely small chance of some validity to astrology.

Those born in September are likely to be the oldest in their school class when growing up, and more mature. Those born in May and June are more likely to be the youngest and less mature. How being younger/older than those you are around probably does have some affect. There have been studies that noted that eldest siblings have some traits (such as being leaders and rebels more often), while middle children have others, and youngest siblings have other traits more often. The effects within a single year are less apparent. But it might have some effects.

So the astrologists might get some things correct just out of dumb luck, even though their reasoning is completely bogus.