Your situation would indeed be frustrating for the vast majority of grown adults.
I lived in a share house situation many years back where the % of shared housework became an issue. We solved it by all contributing to hire a weekly cleaner (this wasn't perfect, but it was better than the alternative).
Hopefully such an arrangement could help your situation. However, this doesn't seem to be to be the crux of the issue for you, because:
- your siblings are taking financial advantage of your parents (not much you can do about this); and
- your parents are consenting to such (not much you can do about that); and
- your siblings aren't as clean as you or your father (not much you can do about that); and
- if they've stayed this long, they are likely going to stay until the day both your parents have passed, or your your father needs full time care.
You note there's not a lot you can do about the above? (which would be frustrating). And quite frankly, were you to say about this - having moved back into your parents home, your siblings would likely throw accusations of hypocrisy at you (whether or not there was ever any any truth to such)
Were I your father, I'd consider having my will made out, donating everything to charity, making sure everyone knew about it (so they could start planning to stand on their own two feet).....because anything else is likely to tear your family apart after your parents both pass.