Don't really understand the end...

Unlike most of the people posting here, I found this film riveting, enjoyable and well directed and acted; but I DO love films that deal primarily with human relationships and behaviour.
My question regards the second last scene, when Olly takes Chris home. He sees Pete walking along the footpath, they look at each other, then Olly sees Pete embracing his (their?) parents in the rear-view mirror of the car.
I guess the three young men are all brothers, but the relationship between the three of them, and with their parents is strange. Why doesn't Olly greet or speak to the parents when he takes Chris home (he had previously spoken twice to his mum on the phone)? And why was Pete living in such straightened circumstances if he is on good terms with his middle-class parents?
Interested to hear your thoughts...
Florio