We finally got to do Christmas with DPS DC and it was great. However, we also ended up looking after DPS nieces when the DC went home. I usually have no problem with this, and I usually enjoy spending time with them. This time was different. We found out that they've been squirreling things belonging to DPS DC out of our house - clothes, underwear, toys or just one piece of a set which is completely useless on its own. They also opened the DC's presents out of their boxes, lost pieces and used all of a brand new unopened painting set.
Dp is from a large family, and is in two minds. He's angry, but he also thinks that toys are for sharing, albeit only if they're opened already.
He has spoken with their parents about the taking things and both swore blind that they had bought these items. We are certain they didn't. It would be a massive coincidence for both sets of children to have ordered the same clothing from where I ordered some of these from - think Etsy and USA, compared to Primark and pepco. I'm not saying that there's anything wrong with the second option and use them myself, but a few of the missing clothing were special ordered for birthdays, and events. Or for the nieces to have the order of a castle but not the actual castle.
And this is the DC's stuff. To me, that's part of making them feel at home here. I think they should be able to say if they want someone playing with their stuff or not, and should be listened to. I agree that sharing is important but I also think ownership is important too.
For background, the nieces parents are separated. One parent has only introduced one partner to them, and that relationship is fairly stable. The other parent has introduced numerous partners, each only lasting a few weeks. The eldest finds this confusing, and is quite an anxious child. She would usually talk to me about how she's feeling about everything.
DPS dsis has also told us that this taking things is an ongoing issue with them, and that they've done the same in most houses they visit. I'll add that this was a completely unplanned sleepover. They literally just landed at the door with these children and asked if they could stay in front of them.
So aibu? And what would you do?