Mostly by just keeping lines of communication open I think.
Me and my brother get on great, but we're crap at keeping in touch. If we lived in the same place, then we'd probably head down the pub once a week or whatever, and see lots of each other. But he lives half way across the country, so we see each other two or 3 times a year, and maybe phone each other once a month or so. He's also not entirely on planet Earth.
Which is why when I saw his camper van turn up on my drive on Good Friday, I was rather surprised. Because I'd spoken to him about a month earlier, and he'd said "We're thinking we might come down sometime in the easter holidays, but I'll let you know closer to the time. And then I'd heard nothing, so assumed it wasn't happening. He on the other hand, had told my Dad they were coming, and expected him to pass on the message. Which he didn't, because he didn't know there was a message to pass on.
So while I was very happy to see my brother, it was rather brief as we'd booked a last minute trip away for a few days. So a couple of hours after he turned up, I left him with the house keys and buggered off!
That would not have happened if my Mum had still been alive, because she was in touch with us every couple of days, she'd have known I was contemplating a trip away and so known to pin down my brother on whether he was coming on not.