How is that Gemini men are possesive?

I know that the zodiac signs say that Geminis don't get possessive and are detached, I know this from my own experience with dating a Gemini once and being hooked onto him for almost 4 years. He never seemed like the jealous type because he seemed alright with it when I went out with one of his friends, but I have come to known that other Geminis I know seem to have the possessive trait in them. Draco Malfoy from Harry Potter and Clay Derby from Copper Sun are both Geminis and they seem to be a little possessive. How is this so if Geminis aren't possessive and detach themselves from anybody else?