Benjy was the son of Stefano and his wife, Ellen Hawk. (Stefano married her using the name David Hadley while he was presumed dead in Salem) Benjy lost his hearing as a child due to an explosion. When Ellen found out what a monster/criminal Stefano really was, she took Benjy and went on the run. Stefano had her killed by his henchman, Iago, who was actually Shane Donovan's twin brother, Drew.
Steve and Kayla encountered Benjy while on their honeymoon and brought him back to Salem. In the meantime, Benjy's grandfather, Orion (Ellen's father), came searching for him, as did Stefano.
In a nutshell, Steve and Kayla loved Benjy and wanted to adopt him. The Bradys embraced him as family, but he eventually left Salem with his grandfather, Orion. Little Benjy was in Salem from 1988 to 1990, so he was heavily involved with the Bradys and other Salemites.
In 2006 he returned to Salem as a young man, now married and with a baby, a son they named Steven after Patch.
Stefano needed a liver transplant and Benjy was kidnapped to be a living donor. Then Andre killed him. Benjy's wife Sonja and baby Steven fled Salem.