I heard that Hino actually modelled the three of them; Kaname, Yuuki and Zero after their zodiac signs, and it's really interesting to see how well they fit Just look;
Pigs are models of sincerity, purity, tolerance, and honor. When you first meet them, Pigs seem too good to be true. They are careful and caring, obliging and chivalrous. Put your trust in him, he won't let you down and he will never try to. The Pigs simply want to do everything right.
Pigs are the people everyone admires most. Make a list of the Pigs in your life: aren't they the nicest, most loving and scrupulously caring people around?
Pigs are born to give, to yield and to serve. Frankly speaking, most people take advantage of this Pig nature. Also, not only are Pigs easy to fool, they like it that way too. No matter how old they get, Pig people still only see and believe that all men/women are basically good. Pig people constantly sacrifice their own happiness and comfort for the sake of somebody else.
Rooster people are very observant. And most of the time, they are very accurate and precise with their observation. Perhaps, you can say that Roosters have a very keen "sixth-sense".
The rooster likes to be noticed and flattered. He might dress a little flashily with this in mind, but in his heart, he is completely conservative. Roosters always appear attractive and beautifully turned out. They are sociable and love to receive attention.
Believe it or not, it is not an easy task to fool the Rooster. His mind is cautious and skeptical, with this perceptive gift.
Rooster make great hosts and adore entertaining. The main virtue in the Rooster character is loyalty: they make devoted friends. They always keep their promises and are always true to their word. When Roosters love and admire someone, they will even catch the moon just to keep them happy.
Dog people are honest, faithful and sincere. They respect tradition and value honor, and enjoy helping people. The Dog is very righteous, and always is the first to speak out against injustice. He is not good at socializing with friends, and rarely shines in company, but he is intelligent, caring and a good listener.
Loyal, faithful and honest, he has the most profound sense of duty. You can count on him and he'll never let you down. And as a good listener, the Dog is also very reliable in keeping secrets for others. He simply doesn't like to gossip.
The Dog is an agreeable companion - when he is in a good mood. But when panic strikes, he can turn nasty, and bark till he is tired. He can be judgmental, defensive and picky if you rub him the wrong way, but as long as you know how to pet and massage him, the Dog makes absolutely the best and most honorable companion on earth.
This is the site the articles are from http://pages.infinit.net/garrick/chinese/ ^^ The descriptions says a whole lot more, I just wrote the beginning.
I'm not entirely sure if Kaname is the rooster, I only heard it once but it seems to match so I took that person's word for it. If you've heard differently however feel free to point it out. He fits the snake alot too. But it's kinda fun how they fit, don't you think? =)