I want a introduction on the relationship between the characters in chapter 4

I'm really not sure what you are looking for here. These characters meet but they they really don't have a relationship. They have relative traits in that they are all issolated and lonely for different reasons. The talk they have in Crooks's little horse room is the best evidence of this. Although Lennie is rather clueless, we understand where he is coming from. The others wear their pain openly.