Every year we fly to the in-laws for Christmas (this could be its own thread).
Every year I make my declaration in writing pre-flight via text to DH and DC x3
”This is my annual declaration that no-one is putting anything into my carry on backpack. This includes but is not limited to - car keys, iPad chargers, water bottles, tissues, packets of lollies (which will be binned), stuffed toys and anything that starts with, “Mum, can you hold this for me”.
DH used to be the worst- he would never carry a bag and would happily load me up with his keys, chargers, tissues and multiple free mini water bottles and biscuits he would grab at the airport lounge. My boundary has forced him to take his own backpack. Funnily enough he doesn’t grab all the free stuff now he has to carry it himself.
I am aware this is all very petty but it’s a great boundary and I recommend it.