Charles is the product of a meeting between Betty Ross and Bruce Banner during a spell of when Bruce had thought the Hulk had been excised from his life completely. Of course, when the Hulk came back as he always does, Bruce ran and left a pregnant (though unknown to him) Betty Ross. Betty, heartbroken, threw herself into her work while Charles' Grandfather, Gen. Thaddeus "Thunderbolt" Ross set about on his quest to capture the Incredible Hulk.
Time went by, and Betty married a psychologist while her true love was on the run from the Military. Bruce occasionally came by to see Charles from a distance, not letting the child know that the man Betty married was not his true father. This all changed, however, when he started puberty. His first day of 6th grade, he was being picked on by a group of bullies.
Normal bullying turned to a beating, and when Charles was on the ground getting kicked, something happened. Charles' eyes turned green, and he grew into a towering green...Hulk. Needless to say, the bullies and the rest of the school were smashed, with Charles making a getaway to a forest about fifty miles away. When he was found three days later by his father of all people, Charles had been hiding in a cave alone, naked, and terrified.When he was brought back home Bruce, Betty, and his stepfather had a long conversation about who Charles' father really was, and why Betty had to keep that from General Ross by getting married, for he would surely either use Charles as bait or, that Charles himself would be Ross' target. Bruce took the blame for the school incident, and Betty spirited him away to the X-Mansion, where he remains today, continuing his education and trying to contain the beast within. Recently, Charles Ross was taken from the X-Mansion by SHIELD and subsequently has joined the ranks of the Avengers. He has since made great strides in controlling the beast within him, and has even learned to switch somewhat at will should the situation warrant it.