I'm honestly on board with hosting people at need. I have a brother interstate, I have a sister and her kids in Gippsland, my parents are in Mornington.

"I'm in town for a thing, can I use your place?" is honestly a really sensible question.

I just...assumed it would be somewhere that I got to use for something when no one else was. A comfy chair and maybe a bookshelf for my National Geographics would have done, so the room wasn't wasted space when I was the only one living there.

No. Parents don't. I don't and have never and never would.

talk, discuss, respect, compromise,

and when parents give something it is the children's to do with as they wish

If the parents want a half share in an apartment they can use they should at minimum have it legal.

And why should Alamut have to pay rates, insurance and expenses on their room?