Gary Sheffield is his mother's only child...and I found no mention of any "other" children his biological father may have had.
"She watches them and wonders if her only child, Gary Sheffield, is Herculean enough to be the scorned man of this baseball season and hold it together."
Gary Antonian Sheffield was born on November 18, 1968, in Tampa, Florida. His mother, Betty, was the older sister of Dwight Gooden, who was just four years older than Gary. Gary’s father owned a pool hall in Tampa. He invited Betty to move in with him, but did not propose marriage. Fiercely independent, the teen chose to raise the boy on her own. Ever since, Gary has had limited contact with his dad.
http://espn.go.com/magazine/vol4no10sheffield.html