Just my POV.
1) For this, personally I feel cannot compare. Some people are more independent and started working early while some only start late. I’m not siding his brother, just that I have 6 siblings so I understand this point. There’s a saying “人比人气死人“. But no doubt, reading on he is indeed a waste of space brat la.
2) I would do it back to him, if his mother has any complaints, ask her to buy for her son again lor. Her son, her responsibity. You already helped her take over her older son’s responsibility alr still expect buy 1 free 1. Technically your husband and you are considered another family, but if he say because you’re staying at their house, everything is their property, then it should be vice versa. Your husband’s family stuffs is also your stuffs 😇.
3) My husband’s older bro does this as well, wash a few times ok close eye. Imagine one coffee cup leave there for 5-6 days then accumulating so many ants, I’m not gonna touch that wtf. Subsequently I just leave it there, his mother can help wash if she finds it eyesore, ITS THEIR HOUSE WHAT. For this I would have told my husband off if he asked me to wash and he can be prepared to wash his(husband) own dishes from then on.
4) Come up with 101 excuses to not collect the food, even food delivery also got comms. Nothing is free, including my service.
Respect works both ways, so if no one is respecting my privacy and efforts, then I won’t continue.