Sly Cooper was born into the lineage of the Cooper Clan under the tutelage of his father, Connor Cooper. Sly grew up learning about his family's history as master thieves and was to follow in his father's footsteps and inheret their legendary legacy, theThievius Raccoonus. On the night Sly was to inheret the book at age eight, a mysterious gang of criminals known as the Fiendish Five infiltrated the Cooper residence. Try as he might, Connor failed to defend himself and his son from the brutes and was killed; the Fiendish Five ransacked the house searching for the book, Sly helplessly watching them while hiding inside the closet. Finding it, they tore out its pages and split it among themselves before leaving, stealing everything from the younger Cooper. Sly, without parents, ended up in an orphanage where he met his lifelong friends, Bentley and Murray. Sly was determined to grow up as an accomplished thief and live up to his namesake.
Sly, as the first describes him, a "cunning, devious, Thievius Raccoonus." He uses his wit, his courage, and his skills to pull off jobs, and he usually has a sarcastic remark in hand. However, he remains loyal and dedicated to his friends; especially Bentley and Murray, his two close friends since childhood, and Carmelita Fox, his love interest. Deep inside that demeanor he holds, it's possible he's a bit lonely, as he said that he misses his father at one point
Bentley's personality changes throughout his life. At a young age he's very quiet, shut in and a bit of a know it all. In the first game he appears happy to help Sly retrieve his family's book but is still panicky, nervous, and uptight. Nonetheless he still manages to pull through in the end and most likely gains confidence from it.
Bentley's greatest and most primary ability is his intelligence. He proves this through all three games by planning every master operation and the plans behind the jobs to accomplish them. He is also extremely skilled with technology, upgrading his wheelchair with various weapons and gadgets as well as inventing numerous devices. Bentley's abilities include hacking.
Murray the Hippo (also called "The Murray", although more by himself than anyone else) started off as a coward in Sly 1.
his love for masked wrestling, and learning that he can put up a fight in the field, made him discover his strength. He is much more bolder, but witnessing Bentley get crippled and his eventual Soul Search gives him compassion and represses his rage to a point where he can call upon it when need be. It is implied by several cut-scenes that Murray is still a child deep down inside mainly due to his unstable behavior.
Like Sly and Bentley, Murray possesses his own abilities. One of his abilities, probably the most important, is his incredible strength and power.
Cooper gang is working for the Society special unit for espionage and stealth mission including stealing information and other valuable thing from the Orgs. Althought, their habit of thievieng and stealing still to be seen.