Whether dogs, cats, horses, whatever - animal companions are members of the family. They are sentient beings and we develop love, friendship, irritation, even dislike towards them, just as we do with the other humans in our lives.
The problem is that our society tends to view animals as our possessions - my pet dog/cat, whatever. But it's beyond doubt that they all have their own personalities, and we develop unique relationships with them. And whatever boundaries we impose upon them, they are never mere possessions.
Mr Frog and I are still getting over the death of our lovely old pusscat Basil. Sometimes when Mr Frog has one of those strange and inexplicable surges of grief over Baz, he'll beat himself up, saying 'But it's just a cat!' And that's the point - he wasn't 'just a cat'.
You and I both know that, Ratter, as do all the others commenting here.