Wuthering Heights explores a variety of kinds of love. Loves on display in the novel include Heathcliff and Catherine's all-consuming passion for each other, which while noble in its purity is also terribly destructive. In contract, the love between Catherine and Edgar is proper and civilized rather than passionate. Theirs is a love of peace and comfort, a socially acceptable love, but it can't stand in the way of Heathcliff and Catherine's more profound (and more violent) connection.
The love between Cathy and Linton is a grotesque exaggeration of that between Catherine and Edgar. While Catherine always seems just a bit too strong for Edgar, Cathy and Linton's love is founded on Linton's weakness—Linton gets Cathy to love him by playing on her desire to protect and mother him. Finally, there's the love between Cathy and Hareton, which seems to balance the traits of the other loves on display. They have the passion of Catherine and Heathcliff without the destructiveness, and the gentleness shared by Edgar and Catherine without the dullness or inequality in power.