Nothing is known about Sonic's early life. It is unknown who his family is or if he has one, neither is it known how Sonic gained his trademark speed. All that is known is that Sonic was born on Christmas Island. It is not even known how he and Dr. Ivo "Eggman" Robotnik became enemies, though it could very possibly be the fact that Eggman is always looking to get more power to be ruler of any land he finds.
Sonic started his battle against his nemesis Dr. Ivo Robotnik when Robotnik wanted to take over the world, but Sonic traveled through South Island freeing the animal residents who were transformed in huge numbers into Robotnik's Badnik slaves and prevented him from getting the Chaos Emeralds. After Sonic defeated Robotnik, he became a well-known hero throughout the world.
Sonic has a care-free attitude, and takes his responsibilities as General lightly. Sonic reacts terribly to being held captive and may find it mentally and perhaps even physically painful. He seems to act absurd if he doesn't run for a long time, which might mean that he is very much addicted to running, and gets frustrated when something is slow.
Sonic is known best for his speed, with the ability to run at speeds greater than Mach 1, which is at the blistering speed of 768 miles per hour. This is evident in many games, where Sonic is recorded to run at speeds faster than 765 mph. It is also stated that "He's the world's fastest, hypersonic hedgehog" which is at a staggering speed of 3,840 mph. He is occasionally referred to as "the fastest thing alive," and can run backwards at full speed just as well as forwards. Due to such speed, he is able to scale right up the walls of buildings, or similar structures, and can also run right over water.
In line with his speed, Sonic has displayed amazing feats of movement and has reaction time to match it. He possesses great acrobatic skills and agility, alongside with astonishing reflexes, making him able to avoid large and small obstacles with precise jumps and delicate movements, despite the speed they are incoming at, and when launched into the air, he can perform several airborne tricks before finally landing on ground. He has also shown on several occasions that he can jump incredible long distances, up to several hundred meters, possibly by applying his speed to his jumps.