There is room for speculation when it comes to the relationship between Lennie and George in John Steinbeck's classic Of Mice and Men. What is meant by room for speculation refers to the rationale behind a friendship so awkward and made of two completely different personalities.
However, we can start by stating that Lennie and George are cousins, and apparently they are the only family each other has. While this is a good reason to suppose that Lennie was important to George, it does not completely answer to the question" "Why?" Yet, this is when speculation begins.
The first motif for their unconventional connection is that they are both loners. They live in isolation from the rest of society and each of the men, in their own unique way, finds it hard to connect with the world. Hence, they enmesh their relationship and look within each other to find that much-needed link to the community.
Second, because they are family and because they have made a form of bond, they look out for each other. In any case, George looks out for Lennie because he knows Lennie cannot not do it alone. After all, they ARE family, and they DO have that bond that secludes them further from the rest of the world.
Finally, Lennie must be important to George because he shares with George the same goal and hope: To own their own farm and move away from everyone. Just by sharing the dream makes the men more connected than ever. After all, they both share half of the dream. Without the two of them together the dream would not be completed.
These are some of the possible reasons why Lennie means so much to George: Their family bond, their common isolation, and their shared dream.