The title of your post is sooooo sad! You’re not losers, at least you have your siblings to share the burden with. I am an only child with a sick father who hoards and a mum who has had to move out, but enables him by going round & cooking him meals!
My dad is also in complete denial that he has a “disorder” and I was thinking of showing him the programme, as I have sky plussed it, but I don’t think he would be receptive. Have you thought about showing it to your mum? It could be a good conversation starter if she is open to it? It is good that you’ve decided to try and talk to her about it, I hope she listens! The key seems to be making them think it was their own idea!
Hope it goes well