First of all, Heatchliff does not have feelings for Hindley, he rather has feelings against Hindley and very strong and negative ones at that. Psychologically speaking, Heathcliff shows a very vengeful sadism against Hindley as he comes back a well off man who manipulates Hindley's gambling and drinking addictions in order to financially ruin him and have him mortgage Wuthering Heights to Heathclif in order to pay off his gambling and drinking debts. This will result in HIndley's death later in the story.