The three love affairs that are contrasted in these chapters are those between Pip and Estella, Herbert Pocket and Clara Barley, and Joe Gargery and Biddy.
The object of Pip's desire, Estella, has been raised to be cruel and heartless, incapable of giving or receiving true love. She is completely upfront with Pip about her nature, telling him that she has "no heart," yet he is infatuated with her, and cannot let her go. Guided by the twisted machinations of Miss Havisham, who adopted Estella as a baby and brought her up, Pip's and Estella's relationship is one-sided, superficial, and doomed from the start (Chapter 29).
A simple but loyal character, Herbert Pocket is mired in familial expectations that he does not quite understand. He wonders that children like himself "of not exactly suitable marriages, are always most particularly anxious to be married," and notes that he and his siblings "are all engaged, except the baby." Herbert's betrothed is Clara, who is "rather below (his) mother's nonsensical family notions," and he actually cannot marry her quite yet, as he has still to "realise Capital," or make enough money to support her. Nonetheless, Herbert's intentions and love are true, and he enlists Pip's aid in realizing "the affair of his heart" (Chapter 30).
The relationship between Joe Gargery and Biddy demonstrates the essence of true love. Joe is a simple man with a great heart, uneducated, yet capable of giving complete devotion and love. Biddy shares the same depth of character, and tactfully guides him in his dealings with the often less than noble Pip. Joe holds a special fondness for Pip, and when he asks her to write to the boy to request an audience with him, Biddy is aware that Pip scorns Joe for his lack of sophistication and inserts a line cautioning him to be kind, saying, "I hope and do not doubt it will be agreeable to see him even though a gentleman, for...he is a worthy worthy man." Joe's and Biddy's love for each other is the opposite of Pip's and Estella's, and a fulfillment of Herbert's and Clara's; it is uncomplicated, totally selfless, and true (Chapter 27).