Why are people in the same constellation somewhat similar in personality?

Actually, I've been thinking about this problem for a long time, and I can't figure it out, but scientifically speaking, it's because the weather, temperature, humidity and other external natural environments are similar when they were born, so it has a certain influence on their brain nerve development (because the number of brain cells has been decided from birth, and then it will only change in size, and the number will no longer increase), so people in the same constellation have similar thinking, so their personalities are also similar.