is a boy's cubby his castle?

Yasin has a large circus tent/cubby in the lounge. It's where he takes his treasures and he does the bolt to there if he doesn't want to co-operate with me or needs a bit of quiet time. Sometimes he likes to have his nap in there. I was just tidying the lounge and I stuck my head in and noticed it was getting a bit messy in there. I was about to tidy it for him and then I thought maybe I should just let it alone - it is his space after all.
He's not allowed to have food in there so it's messy but not dirty and since it has flaps at the doorway the mess is hidden and doesn't impact on the lounge.
Now that he's 3 is he old enough to start taking responsibility for his space or am I expecting too much? Of course I understand that he needs help/guidance with tidying.
How old were your children when they started helping to tidy thier own spaces?
TBH if I can drop something from my cleaning list I'll be happy lol.

Hmmmm neither of my 2 boys will willingly clean up their toys. They hate the idea of it.
Maybe you could start off but asking him to organise all his things into piles, so all his cars together, soft toys together etc. Just so he gets an idea of giving things a place. Help him see how having things tidy gives him more room to play.
I have started to make it a rule now that before another messy toy can come out the others have to be put back (blocks or trains that sort of thing) and they are getting the hang of it. I am also going to make Evan a list of Jobs I would like him to do. He likes to have a Job & is the Helper at preschool etc so I think if I work it in right I could make him feel pretty special about having his own jobs at home also. Just need to think of the ones that I know he can do.

Seth has to help Paris pick up his toys now. And if he doesn't help he doesn't get to play with anything else. I know I'm an ogre, but we make it a game and he's fine he loves it. I made the mistake with Paris by not getting her to help out till she was over 3, I won't do that with Seth LOL! I probably am slightly more focused with Seth because Paris is naturally neat, whereas I don't want Seth to be someone else's problem when he's older iykwim?

When i'm clean up things that need to be thrown out i get Lily to help me by asking her to see how many things she can pick up(this also helps with her counting). In regards to her bedroom though i have a hard time with this. DH tidied it all up on Monday but now all her toys are everywhere again. i ask her to pick them up by counting how many she can but not 10mins later its messy again.

I'd get Yasin to learn about keeping his area clean and tidy, that if he doesn't then mummy will come in and clean and move things around. Even if you get funky plastic boxes for him to keep things in (so they can double as tables or play areas).

my brother & SIL had the kids playroom, which was separate from their rooms (it was an extension off the side of the house with sliding doors from each kids room), which was the kids responsibility to keep tidy and they knew that if they didn't pick up the toys then it didn't get cleaned on cleaning day and was then out of bounds until they cleaned it (we used to lock the doors and they had to ask to go and clean it so they could play - it took about 4 or 5 times of not being able to play before they got the idea of putting things away).

DH's boys are grots, their mother never made them clean up after themselves and now 2 of them are teenagers I pity the poor female they end up with, DH used to try to get them to clean but what they did at "Dads house" was undone when they got home.

We have just started getting DSD (4yr) to tidy up after herself. I wish we had started when she was younger. I think it would have been easier.