In the novel, Jane Eyre, Jane and St John are similar in that they both live to serve. Jane has spent her life as a servant. She worked in the orphanage and then at Thornfield. St John severs the church and God.
Another characteristic the two share is that they have good intentions. Jane is kind and giving as evidenced in her treatment of others. St. John wants to help others, too. St. John's desire to marry Jane is to keep her safe and save her soul.