Thanks for the responses and the advice. I hadn't actually thought to consult my doctor though I feel like he wouldn't be able to help (however I've only ever consulted doctors for physical problems), he even might be able to direct me to someone who can.
Also maybe I just need to vent my frustration so here's me venting..
A little backstory on the issue.. My grandparents are getting on in the years and as a nice thing for them, my parents paid for them to go see family over in England. They loved it and it was one of the best experiences for them as they hadn't seen the family over there in forever.
While they were over there, my uncle (who was living in Japan) came into financial difficulties though at the time not admitting it to the family. So while my grandparents were out of the country and my parents not living in the same state as my grandparents, my uncle and his wife moved into my grandparents place back in Perth to look after it.
Fast forward 4 years and my uncle and aunt are still living in my grandparents tiny unit (one of them pulls out a mattress each night to sleep on). My grandparents are old and even though they have tried to get them to leave (many many arguments), they've just resigned themselves to defeat, fully expecting them to be there for the rest of their lives.
Sure I can understand them staying for a while but now it's like they're waiting for my grandparents (who I absolutely adore and hope they live forever) to die to move into their home fully. My brother and I aren't well off though we get by... we work terrible jobs and rent a slightly larger unit than my grandparents. It makes my blood boil every time I think about them now and there's nothing I can say or do to get them to leave. My grandparents, my brother and I regularly catch up for afternoon tea and dinners and it's come to a point where they prefer coming over to our place just to avoid my Uncle and Aunt.
They won't listen to my grandparents. They won't listen to my mother who's also feeling the same as me, if not worse as she's in another state. And they won't listen to my brother or myself.
I don't know what to do.. :(
It helped a bit to type this, so thanks for enduring my rant.