Harlen Bigbear is Will's best friend and the impetus for many of the events in the novel. He's known for being involved in everyone's lives and as a prominent—if nosy—community member. King writes that

Harlen went to everything. He went to all the powwows. He went to all the funerals. He went to all the weddings, the births, and most of the court cases. Any time there was a gathering of two or more Indians in a hundred-mile radius of Medicine River, chances were one of them was Harlen.

Another important quote is from an exchange between Harlen and Will early in the book. It helps show how Will sees Medicine River in the wake of his mother's death. King writes:

"So, when you think you’ll be moving back home?"
"Here?"
"Sure. Most of us figured that, with your mother and all, you’d be coming home soon."
There was no logic in it, but my stomach tightened when Harlen said home.

It's difficult for Will to identify a home because his family was forced to leave Medicine River, since his Mom married a white man. He and his brother, James, are not considered Indian. King writes:

"We going back to the reserve?" James asked.
"Maybe," I said.
"No," said Maxwell, "you can't. You guys have to live in town cause you're not Indian any more."
"Sure we are," I said. "Same as you."
"Your mother married a white."
"Our father's dead."
"Doesn't matter." I could feel my face get hot. "We can go to the reserve whenever we want. We can get in a car and go right out to Standoff."
"Sure," said Maxwell. "You can do that. But you can't stay. It's the law."

This is one of the incidents that causes Will to struggle with his Blackfoot heritage. He doesn't see himself as a complete member accepted by the community at Medicine River. He's also unable to associate himself with his father, who he barely knew. King shows over and over how unfamiliar Will is with his father, even when compared to the other people in Medicine River. He writes:

"You ever see your father rodeo, Will?"
"No, he took off when I was about four."
"He and George Harley were good friends. George says your father was a real good bronc rider."

Will, however, chooses to act as a father to Wilma, Louise's daughter. He takes her to the hospital, stays, and helps come up with a nickname for the baby. King writes, "I'll bet you have a name all picked out for her." Then continues with Will's response as he says, "'Yeah,' I said, feeling really good with the baby in my arms, 'we'll probably call her South Wing.'"