1. Nick's relationship with his dad is compliant. Nick follows his dad seemingly without argument to a remote Indian camp to assist his father in a difficult delivery. From Nick's questions, readers infer that Nick went along with his dad before even knowing what their mission was, and from Nick's lack of excitement when his dad answers his question, Hemingway demonstrates that Nick is used to simply going along with this dad.
2. Their relationship is also a typical father-son relationship. Nick's father becomes so engrossed in his difficult task that he forgets that his young son is witnessing the quite horrific events, but when he does come down from his adrenaline rush from successfully delivering the child, he realizes that Nick is not doing so well and attempts in his own way to comfort him.
3. Finally the father-son relationship is honest. Nick obviously feels comfortable enough to ask his dad anything (i.e., after the Indian husband's suicide, he asks his father if dying is hard), and Nick's dad thoughtfully offers concise but honest answers.