If you had remembered that Hareton was your cousin as much as Master Heathcliff, you would have felt how improper it was to behave in that way. At least, it was praiseworthy ambition for him to desire to be as accomplished as Linton; and probably he did not learn merely to show off: you had made him ashamed of his ignorance before, I have no doubt; and he wished to remedy it and please you. 
Hareton is your cousin; and it was a praiseworthy ambition for him to wish to learn to read. Probably he did not learn merely to show off: you had made him ashamed of his ignorance, I have no doubt; and he wished to remedy it and to please you. 