Who is He?

So Tuesday night, I notice that the daughter and boyfriend come over with their little pug - Goblin. Such a strange dog for them. She is in her usual flowing black layers with her messenger bag that has rubber spikes sticking out the front. And the boyfriend has gone all retro and has his hair greased ala Fonzie style, or maybe I'm thinking more like Danny Zuko from Grease - you get the idea, well at least the era. A moment before, I noticed the son had come home and before heading up to the studio apartment, was petting the cat who was laying belly up on the driveway (she runs away anytime I try to come near her - she spends time over in our garden a bit). The daughter seemed in good spirits and the boyfriend was jolly. I noticed the son had come down and was talking with the boyfriend. So that at least takes care of the doubt that I had that maybe they were one and the same person - they look a bit similar - same height and style of dress. Although the son is more quiet and timid. I think they ended up having dinner together but I got the impression the son wasn't part of the festivities. He really does look like the daughter, so I do think he's the son, at least the brother, but why wasn't he eating with them. Does he not eat? I've never seen him partake in any of the meals, inside or outside. He had weird body language with the boyfriend too. A bit uncomfortable. Maybe he did something earlier in life that hurt the family and now is slowly returning to the family fold. The only person I've seen him comfortable and at ease around was the cat - which I guess doesn't count since she isn't a person.