Or is my brother (trivial but am about to throttle him)

[overthinking]

He's staying with us - they don't have kids.
Everything has to be on his timescale. So in the morning, he refuses to get up before 9am, then takes at least an hour and a half to get ready. He moaned yesterday that we had lunch too early (12pm) and then today moaned that we had lunch too late (1.15pm)
We're due to go out for a meal tonight with my parents, and he's said he's not eating until at least half seven as we had lunch too late (that would mean the kids going to bed at gone nine.)
He's also taken over our entire lounge with his stuff, won't put it in his room cos he 'needs' it.
WIBU to poke him in the eye?

YANBU at all! Poke away. Also, eat when you want, if he wants a different meal time, tell him to get off his arse and make his own breakfast/lunch/dinner.

Gather up his stuff in a basket (with very little care!) and dump it on his bed.

I hope, for your sake, that his visit is a short one! A poke in the eye would be well-deserved IMO! Suggest you stop catering for him, since your mealtimes don't suit him, and claim back your lounge ASAP.

If it was my brother I'd just bundle his stuff up and put it in his room! And tell your parents you can't eat too late because of the kids. I'd just not take any nonsense.

If he's your brother you must revert back to childhood immediately. Start squabbling with him; call him names, roll on the floor fighting & steal his Action man. Then tell your mum how mean he is.
He'll soon be begging to leave!

YANU to tell him that when he has his own home he can do as he pleases.

and put his stuff outside.

How old is he - 5?

Tell him your family eat when it's suitable for your children, not a grown man behaving with less maturity than your DC.

Would also suggest you tell him he's behaving like a complete tit.

I very rarely see him as they live abroad, and I haven't lived with him for over 20 years - but he drives me mad! I don't know if it's just cos he doesn't have kids!
He's also bloody fussy about what he eats, because he doesn't like British food
I will grin and bear to keep the peace - thanks for letting me offload!

Is there any reason that he has to be up before 9 am? And 12 o'clock is quite early for lunch. Although he is being a bit unreasonable about refusing to eat before 7.30

Can't you get your kids to play with his stuff? Or I can send mine over. He'd never leave anything out again.

Well, I probably wouldn't care about when he got up etc. (as long as he wasn't hogging the bathroom when I wanted to use it). I'd keep to my own/DC's schedule for mealtimes, if he wanted to eat at different times I'd just point him in the direction of the kitchen to see to himself.

But - "He's also taken over our entire lounge with his stuff, won't put it in his room cos he 'needs' it."
Nope, nobody gets to do that. I'd just gather it all up and dump it in his room, preferably where he would trip over it [evil]. What kind of stuff?

Sod that!
Point him in the direction of a hotel and bolt the door. Numpty.