Greg is an easy-going 50-something year old whom Wild intended to be the opposite of Jake: an intelligent, sympathetic man who actually listens to other people.
Warning: The following may contain plot or ending details.
Though always an instructor himself, Greg meets Helen when they are both students in Amanda Lane's art class in "Breaking the Mold." There, Greg helps Helen gain confidence and self expression through her sculpting.
Afterward, Helen takes it further and joins one of Greg's sculpting classes, which she alludes to in "Erin the Head." In "An Uneasy Marriage," Jake gets so jealous of the amount of time Helen spends with him, in sculpting class and out, that he joins the class to keep an eye on them. There, he observes that Helen and Greg have an easy-going rapport, and that Greg is a sympathetic listener. When Jake finally confronts Greg about his interest, Greg admits that Helen's "ugly and dark" sculptures drew him to her, as they suggested a deeply confused, angry, unhappy person inside. After learning of this conversation, Helen confronts Greg herself. She is prepared to leave his art class altogether, but instead finds herself confiding her deepest, darkest fears about her marriage to Jake. Greg comforts her with an embrace... and then they kiss.
From that point onward, Helen avoids Greg. She decides against calling him in "All But Forgotten" and does not visit him even after learning that he has taken home the sculptures that she abandoned. Greg attempts to contact Helen a couple of times, but Helen does not respond. Jake, however, continues to hold the kiss against her, having learned about it in "Memory Road." Only after she and Jake have reached a better understanding does Helen finally respond to Greg, and in "Tomorrow Never Knows," she learns that he entered her sculptures in an art show. Helen decides to go out with him and discuss artwork, with the subtle implication that there could be more interaction down the road.
It is unclear whether Greg has always been physically attracted to Helen, or whether the attraction began shortly before their kiss in "An Uneasy Marriage."
"You seem to have made something that captures people's interest. Maybe you're not the poor sculptor you thought you were." -- "Breaking the Mold"