Why was the prodigal son spoken harshly of by his elder brother?

In the parable of the Prodigal Son, Jesus narrates : "Not long after that, the younger son got together all he had, set off for a distant country and there squandered his wealth in wild living" (Lk 15:13) But, when the prodigal son returns home to a warm welcome, his elder brother comments to his father :".. when this son of yours who has squandered your property with prostitutes comes home, you kill the fattened calf for him!". One is amused by the remarks of the elder son with reference to the off-home stay of his younger brother, which in fact, was not the narrative given by the story-teller (Jesus). My question is: was Jesus intending to bring out the degeneration of relations over property and wealth by 'making' the elder son speak harshly of the younger one ? Are there some commentaries available on this subject ?