While not the main character in the games, the U.S. cartoon (which combines elements of the games with the live-action movie) places him as the leader of the Street Fighters, making him the main character.
Guile is married to Jane, the sister of Eliza Masters, the wife of Ken and has a daughter named Amy. They often appeal to Guile not to kill M. Bison in his endings, worried that he would lose his way if he did. His love for them makes him spare Bison.
In the live-action movie and U.S. cartoon, his full name is William F. Guile. Capcom did not canonize the name however, so it's just Guile.