How is the relationship between George and Lennie presented in Of Mice and Men?

In Steinbeck's novella Of Mice and Men, George and Lennie have a complicated relationship. George often insults and chastises Lennie for Lennie's many mistakes, most of which tend to have quite serious consequences. Lennie does not, however, dislike or resent George for these interactions. Rather, Lennie relies on George for his guidance, both through these redirections and George's ability to imagine their hypothetical future. 

Although they are both physically grown men, these aspects give their relationship the quality of a parent-child relationship rather than a fraternal or friendly one. What is interesting about this fact is that George and Lennie are not in fact related. They simply travel together, and George cares for and guides Lennie. One can analyze this situation and understand that despite George's many negative interactions with Lennie, he actually cares for him very deeply and worries about his well-being. In return, Lennie loves George with the unbridled adoration of a child.