Catherine and Heathcliff's passion for one another seems to be the centre of Wuthering Heights, given that it is stronger and more lasting than any other emotion displayed in the novel, and that it is the source of most of the major conflicts that structure the novel's plot.
I think that Nelly might have something to do with H and C's tragic love story as she criticises them harshly, but this passion is obviously one of the most compelling and memorable aspects of the book. It is not easy to decide whether Bronte intends the reader to condemn these lovers as blameworthy or to idealize them as romantic heroes.
Class status may be responsible for keeping Heathcliffe and Catherine apart. Catherine's decision to marry Edgar so that she will be "the greatest women of the neighbourhood- is only the most obvious example. The shifting nature of social class is demonstrated by Heathcliffe from being a homeless orphan to a young gentleman by adoption to a common labourer to a gentleman again. .
Catherine and Heathcliff's love, on the other hand, is good in their childhood but is harsh on Heathcliff when Catherine chooses to marry Edgar. In choosing to marry Edgar, Catherine seeks a more gentle life, but she refuses to adapt to her role as wife, either by sacrificing Heathcliff or embracing Edgar. .
Catherine and Heathcliffe who loved each other never were destined to be together because they were first seperated by Catherine's marriage to Edgar Linton and then Catherines death. What resulted from their longing to be together was only violence.