The younger sister is wearing her brother's pants (and they fit and will be highwaters on her before him). The brother wore his younger sister's shirt. And it fit. (It was black. He absolutely would not wear pink but he had on her black long sleeve shirt for a couple days last week.)
This wasn't a problem with two boys. #1 and #2 would swap clothes all the time. #4 and #5 seem to be swapping clothes and both have a touch of embarrassment when they have each other's clothes on. But not enough embarrassment to march themselves upstairs to change their clothes.
Today the girl doesn't care. She has on his pants and she wants to go outside and she just does not care.
I foresee screaming.