The Friar rebukes Romeo for falling in love too quickly. Only days earlier, the Friar says, he was in love with Rosaline. Now he is in love with Juliet, which the Friar interprets as the fickleness of youth:
Holy Saint Francis! What a change is here!
Is Rosaline, that thou didst love so dear,
So soon forsaken? Young men's love then lies
Not truly in their hearts, but in their eyes.
Romeo's affection for Juliet, the Friar claims, is superficial, just as his professed love for Rosaline was. When Romeo observes that the Friar often chided him for his love for Rosaline, and points out that Rosaline, unlike Juliet, did not return his love, the Friar retorts that Rosaline knew well that Romeo's love was not sincere:
O, she knew well
Thy love did read by rote, and could not spell.
Despite his rebukes, however, the Friar supports Romeo in the hopes that his union with Juliet might end the destructive feud between their two families.
i think friar rebuked him because of his family