Centaur's are half human on top and half horse on the bottom. They are with the head in the stars, with the legs on the earth. They want higher aims, than a normal human wants - but are fixed to the ground at the same tame. They hate that, cause they don't want any chains, they want to be free, always do whatever is coming to their mind.
According to the legend, Zeus enlisted in the shape of a swan to the beautiful Leda - the result was their son Pollux. The same evening she and her husband fathered a child also. Pollux and Castor was born as twins and were very close to each other. Both were very strong and brave - Castor was mortal, but not Pollux. When Castor was killed in a fight, Pollux begged his father to send him to the underworld also. Zeus placed him before the election, either to live alone in the Mount Olympus or to commute with Castor between the underworld and heaven. Pollux chose the brother and they both live alternately with the gods and under the earth.
Twins are with the head often that high in the clouds - but often as down like they would be under the earth. In one moment the are happy and in the next aggressive. Due to this they are impossible to handle for longer. They are born Casanovas - but for staying longer then just one night, you have to be a riddle to the twin and surprise him again and again, allthough twins place great emphasis on human relationships. But when they've found his "twin" they would follow him everywhere - even in the underworld.