Oh, astrology fails entirely; I was simply bringing up that the idea of the month of birth having some effect on personality has some merit, and that is also one of the most basic precepts of astrology (even a broken clock, eh?).

But like you said, there are many factors in personality, from genetics to name to birth order, etc. In fact, the very fact that one is a twin is going to influence a twin's personality.

And I also want to make the point that one should not dismiss pseudoscience or non-scientific cultural practices out of hand, because oftentimes there is some sort of rational basis for since pieces of those beliefs. Not always, but a huge amount of modern medicine is built on the practice of ethnobotany, which is effectively applying the scientific method to traditional medicines from around the world.