Ineed that is bad, saying that though, when my sc's came to stay they knew it was my ds's room, he got so pissed off with things being stolen and sold at the sc's school (and I'm on about a psp, Xbox games ect, I basically had to do a bag check before they left) that he wrote a note saying please don't steal my stuff.. I didn't know how to respond to that in all fairness 
But they came the weekends he was either at his dads or paternal GP's, so they had a bed each, I couldn't unfortunately put sd in my dd's room as a care leaver she had had enough of her possessions broken and stolen so there was a lock on her door.
Everything in the house that was a shared item they were allowed to use as much as anyone else and we also got them their own things games consoles ect, their own wardrobes even though we're stuck for space as I refused to let them live out of a bin bag all weekend.
They would argue between themselves a lot and fight over who was sat or stood next to p, and were violent (I didn't know this till recently how bad) to little DS but passed it off as rough housing and I thought he was being over sensitive until one day I actually saw what was going on with my own eyes.
I put it down to the fractured relationship between them and both parents, it didn't stop me resenting or being pissed at the behaviour, but I laid the blame firmly as their parents feet. They were just children. Damaged, fragile, children.
Upon returning to live with their mother for example they were encouraged to be vile to both p and myself, which they did, but it backfired when they also were vile to their mum. She didn't like them apples, I assure you.
When contact with p began again we both had to swallow the extremely cruel and nasty messages they had sent when they left, and try to get back to normal.
Contact was encouraged by their mum to be ad hoc which played havoc here as I was expected to be the taxi service and also take the lead role in their care. As I said up thread, I often spent money I hadn't got to get them clothes and shoes, I am separated from p and he didn't seem to feel the need to contribute, I simply facilitated contact as there was nowhere else for them to go, and they needed to see DS. Half of the things that I planned for weekends with DS were binned on these weekends as too childish for them or something they didn't fancy doing. And would whine all the way through if we did go. One wanted to be on a tablet all weekend, the other on the xbox, lounging around on my bed with his shoes on, refusing to take them off, giving no reason as to why. Infuriating, lol.
P was Classic Disney .. I won't go into that.
He wouldn't fund his Disney crap though 
I had to.
It continued like that until one weekend he told sd off for something ss had goaded her into, she then refused to come, shortly after that, DS disclosed he had been sexually abused by ss. And that was that. I won't have them here again, well, sd isn't an issue, she is still welcome, but I have encouraged p to have contact with ss, the boy still needs his father, it won't be here though, and apart from taking him to a hotel, there is nowhere else overnight contact could take place with the situation p is in ATM.
I think I gave them the best of myself that I had to give. It's been thrown back in my face. I'm not angry though, about that. I'm angry that ss abused my four year old son, as an adult I can hold together my feelings about anything else.
I find it all incredibly sad because I know that things are unlikely to change for them. They will grow up damaged adults.
Really I am better off if I disengage from it all.