What is Pavel and Peter's story? How relevant is the story to the story of Jim and Antonia?

These two bachelors live and work together. They become friends with the Shimerdas because they speak a similar dialect. After Pavel dies and tells a shocking story on his deathbed, Peter is brokenhearted and moves away. I suppose Antonia and Jim follow a similar line of friendship. Also there is heartbreak involved with Antonia and Jim as well.