Greg was born in Toronto. Greg's mother, Terrea Oster, is a teacher. His father, Maurice, is a film director, Greg firmly states he wasn't just "put" in his father's movies, but earned roles on his own. Greg has also said his grandfather was an actor, so acting definitely runs in his blood.
His mother has also done some acting.
Greg's parents separated when he was twelve. He maintains a healthy relationship with his father and mother. Since both of his parents reside in Canada, he only sees them a couple of times a year.
Because of his acting, Greg has traveled all over the world. He's lived and filmed in Romania, Los Angeles, and Texas. He now resides in Utah, near the set of Everwood.