Elder Brother
I think that the elder brother had influence from outside in some way and because that was a threat to the rest of the family, the father killed him.
shareThe outside brother didnt exist..... he was one way for the parents [or adults] to control the children/teenagers.
The male adult put red ink on his shirt and ripped it himself.
Regarding the question of whether the missing brother really existed:
I recently read an old interview of the director where he was asked about that and he replied that THE BROTHER DID INDEED EXIST. He went on to say that it would make no sense for the parents to have fabricated a story like that, as that would give the children the idea that life is possible out there and maybe they could run away too.
Yea that's why the father get excited about the cat. So he can have that brother 'killed' by the cat so he wouldn't have to fabricate any more stories about him.
It's probably his escape too that makes the parents are as protective as it is