DSC are 8 and 9. They are lovely and we get on great but they do things that I wouldn't accept from my DC and that DP would tell our kids off for, but he doesn't say a word to DSC. For example - they don't tidy up after themselves, they don't help at all (I.e. Clearing own cups/plates), they do silly things - the latest is drawing on all the apples and grapes in permanent marker - which our DC would've got a massive lecture about wasting food for, they don't sit still at the table, they have no table manners etc. This weekend they wasted about£20 worth of food by ddumping it in sandy water when playing spies. DP merely said to me he'd give me the money to replace it.
DSC have also done more dangeroustthings recently - like putting and leaving our baby on the kitchen table and jumping out in front of a car then back onto the pavement. DP said very little. Our DC look bewildered as to why DSC do not get reprimanded and I can foresee much resentment. DP wworries they'll no longer visit if he tells them off but it's getting ridiculous now - they need some boundaries and responsibilities.
When I've discussed it with DP he says he will tidy up after them/replace damaged things and said he doesn't understand when I say he's missing the point. AIBU to resent him for this?