What is the relationship between George and Lennie, in Of Mice and Men?

George and Lennie are friends in Of Mice and
Men. George takes on a father-figure role toward Lennie. George ends up being
the care-taker from the beginning and throughout the book. He has to ensure Lennie is
treated fairly (when the boss wants Lennie to talk, and when Curley wants to beat Lennie
up) and follows rules of society (Lennie needs to understand when it is okay to touch
people, and if and when it is appropriate to bring animals into the
bunkhouse).

Lennie does provide George the fulfillment of
George knowing that he is contributing to the world, however, Lennie's disabilities
ultimately become too much for George to handle.

This story
is truly a story about the lengths to which one will go in order to do what is best for
a friend.