Ah yes. ‘I’m willing to compromise, as long as you acknowledge that I’m entirely right and you’re entirely wrong.’
True. What about the person who spends a few hundred buying the kids an on-sale swing set on impulse, when there’s still plenty of money left over for the rent; versus the one who wants to spend three months studying the issue, by which time the sale and the summer are both over?
Those two need to sit down together and a) determine an amount of money over which either’s supposed to consult with the other before spending b) figure out some sort of guidelines as to how long is reasonable to spend consulting for approximately how much expenditure. And, probably, discuss how important it is that their kids get a swingset. If either one keeps insisting that it’s entirely the other one causing all the friction, it’s not going to help.
But the person who expects everybody else to always show up within a specified five-minute interval is annoying those who don’t work that way. If circumstances genuinely require showing up in that fashion, they’re justified. But if not, why is the person who wants exact timekeeping the only one whose annoyance matters?
Depends. Did they say ‘we really want you to be here by 10!’ or did @Little_Nemo suggest 10 and not discuss whether they needed to be ready by then? Is Little_Nemo going to hang around at the mall with them until time to head home, and is just as happy to hang around at the brother’s? Does Little_Nemo need or strongly want to be someplace else entirely by 11? And if Little_Nemo, who’s the one actually doing the driving, doesn’t care, why does the brother, and why do you?
That’s my problem, not theirs. If I knew clearly when the thing was going to start, I can either go to the extra lengths necessary for me to make sure I get there on time, or I can take my chances on whether I’ll miss part of the event or even not be able to get in. Or, of course, I can say ‘no thanks’ and not show up at all.
When it’s appropriate, I’ve sometimes set up backup plans – ‘Sister, what do you want me to do if I get there (a five hour drive) after you leave for X? Can we set up a way for me to get into your house, or do you want to give me directions for how to get to X on my own (if it’s something I can sneak in late to)?’
(Accommodations in my family go both ways. I host Thanksgiving; and we now have Thanksgiving dinner on Friday. They come here, arriving on the Thursday, and stay for a couple of days; and after several years in which they couldn’t manage to get here anywhere near on time for the traditional Thursday dinner, I finally got my brain functioning on the subject and said we’d have Thanksgiving on Friday, and a much more casual whenever-people-get-here-and-eat-first-if-you-get-too-hungry meal Thursday evening. Works fine.)