Why does someone have two constellations?

No matter who has only one constellation, and the constellation is calculated according to the date of the new calendar, it is impossible to change every year like the old calendar! I think: the so-called "two constellations" may be his own constellation, and the other is his personality and behavior, indicating that there are similarities or acquaintances with another constellation, which may lead to two constellations! ! This is my opinion.