In all versions of Final Fantasy VII, from the original game to the ongoing remake, a great strength of the story is its unique cast of characters. Even the ones that don't get as much focus have distinct personalities and rich backstories.
The Chinese zodiac is based on the lunar calendar and a twelve-year cycle, in which each year is represented by an animal. Based on the timeline given in the Final Fantasy VII 10th Anniversary Ultimania, these are the zodiac signs of Final Fantasy VII''s nine playable heroes.
Cid Highwind - Rabbit
Born in 1975 in the beginning of the Year of the Rabbit, Final Fantasy VII's incarnation of Cid is not quite as sensitive and polite as the typical Rabbit sign. He is loud, brash, and often crude: it isn't likely that he would back down from an argument. However, underneath his gruff exterior, Cid is a deeply compassionate and kind person.
He is unwilling to sacrifice Shera's life to achieve his ultimate dream of going to space and fully willing to step up and temporarily lead the party when Cloud is incapacitated, speaking to his strong sense of responsibility. One of the Rabbit's lucky colors is blue, fitting with Cid's ever-present blue jacket.
Vincent Valentine - Tiger
Born in October 1950, Year of the Tiger, Vincent more than lives up to the reputation of power that Tiger signs have. While they can be sullen and gloomy at times, Tiger signs are highly independent and natural leaders and protectors. They are associated with the banishment of evil.
Vincent's possession by the demon Chaos and the monstrous forms he can take as a result are, ironically, the powers he uses to fight evil. His betrayal, murder, and self-imposed exile from society have made him withdrawn and stoic, but he retains his fearlessness and sense of justice. He not only fights to save the planet in the original game, but does it all over again in his spinoff title, Dirge of Cerberus.
Cait Sith - Rat
Found in Gold Saucer, Cait Sith is a cheerful cat who rides a large Moogle into battle alongside the party. However, it's revealed that Cait Sith is a machine who was not born. His operator and true identity, Reeve Tuesti, was born in 1972, Year of the Rat. (As any fan of Fruits Basket knows, the Cat is not a true zodiac member).
Rat signs are known for prosperity and wealth, as well as intelligence and tendency to wait for the right opportunity instead of pressing recklessly ahead. Reeve, a Shinra executive who is smart enough to create Cait Sith and use it for espionage, checks off every box on that list.
Yuffie Kisaragi - Goat
Born in the Year of the Goat, 1991, Yuffie is just as stubborn and passionate as her sign would indicate. While she isn't physically very strong, she is clever, aims high in her goals, and is very resilient, all qualities which still hold strong even when she appears in Kingdom Hearts.
In Chinese tradition, the Goat is also a symbol of filial piety. Though Yuffie is at odds with her father Godo throughout most of the game, it is only because she disagrees with his response to Shinra's dominion of Wutai. She does what she does because she wants the best for him and for their country.
Red XIII/Nanaki - Pig
Red, as it happens, is an unlucky color for those born in the Year of the Pig. Given the name Nanaki when he was born in 1959, he was branded with the moniker Red XIII when he was captured by Shinra and used in experiments. In addition, he loses both his parents at a young age and spends years erroneously believing the worst of his father Seto.
Despite his run of tragedy and bad luck, Nanaki embodies the best traits of his sign. Pigs are logical thinkers, determined providers, and good at problem solving. Nanaki approaches problems with a narrow, straightforward way of thinking (though he is not ashamed to admit when he is wrong), and takes his position as protector of Cosmo Canyon incredibly seriously.
Barret Wallace - Rat
Like Reeve, Barret was born in 1972 in the Year of the Rat. He is a natural leader who won the complete trust of AVALANCHE's members with his dedication to their goal. Growing up poor in the mining town of Corel and seeing the Shinra Company abusing the people and planet alike made him devote his life to taking down the company to create a better world by any means necessary.
Also in keeping with Rat characteristics, Barret can have a short temper and lacks patience at times. He does not give out his approval freely, but once someone has it, he will have their back through thick and thin, as seen in the development of his friendship with Cloud.
Tifa Lockhart - Rabbit
Like Cid, Tifa is a Rabbit sign, born in 1987. She is every bit as witty, compassionate, and quick on her feet as her sign would suggest, making her one of the best characters in Final Fantasy VII. Though she doesn't have the huge weapons or superhuman abilities that most of her comrades do, she more than makes up for it with her martial arts skills and sheer determination.
Though every Final Fantasy VII hero is driven by love in some sense, Tifa in particular is fuelled by the desire to protect the people she loves. Like most Rabbits, she is intensely loyal and will never abandon a friend in need, as seen when she temporarily leaves the party to care for a comatose Cloud in Mideel.
Aerith Gainsborough - Ox
With her birthday landing in February 1985, Aerith was born at the beginning of the Year of the Ox. As befits her sign, she is down-to-earth, hardworking, and honest. Despite being outspoken, she tends to keep her most personal feelings to herself, and always makes plans before taking drastic action. This is best (and most tragically) shown when she leaves the party to call down Holy in the Forgotten City, without telling anyone where she is going.
Just as the Ox is the strongest of the zodiac animals, Aerith is one of the strongest members of the party, with her Cetra blood giving her power and a connection to the planet that no other person alive has. Incidentally, Ox signs are most romantically compatible with Rat signs: such as her long-lost boyfriend, Zack Fair, who was born just a year before her.
Cloud Strife - Tiger
Cloud shares not only several characteristics with Vincent but also a zodiac sign: born in 1986, he is a Tiger as well. He is a strong and reliable leader of the party: while rarely planning too far into the future, he is highly adaptable and can lead his friends through any danger. He is protective of those he loves and willing to do anything to save them if they are in trouble.
Much like Geralt of Rivia in The Witcher, Cloud is also incredibly resilient, never permanently taken down by even the most devastating blows. He has survived the burning of his hometown by Sephiroth, experimental Mako infusion (which made his eyes glow the Tiger's lucky color, blue), bouts of amnesia and dissociation, a personality-reconstructing coma, the deaths of his mother and best friends, and several other traumas, but still always manages to get back up and keep fighting.