Haha, sometimes things turn out funny like that :D
But visiting your sister sounds like a generally great plan :)

Yeah; I was supposed to go last weekend and didn't make it. High time!

Eek, sounds tedious! I'm within driving distance of my grandfather and parents, but my brother is in another city now that's about 1h away

Oh, that's not so far! How wonderful!
I've got some family in the same town but all of my siblings are a distance. One's a two-and-a-half-to-three-hour train trip (my brother), one's an eight-hour train trip (my younger sister), and one is a two-day train trip (my older sister).
Mostly I have to fly when going to my older sister, which is never fun, but what would you? It's just so long otherwise.

My sister and father are around the same distance from me as your brother from you (close to each other, which is really nice, since I can visit them all at once that way). My mom is 6 and a half hours by train or one hour by flight.
I'd definitely fly instead of going on a two-day train trip, I actually fly to visit my mother most of the time... Everything over 4 hours on the train starts really getting at me. But the 6 and a half are still bearable, I've done that a few times, too.

I kind of like the train trip to see my younger sister. Everyone knows you're travelling that day so you don't have to deal with a lot of demands, and that's most of a day that you can actually sit down and get some uninterrupted work done. Take a project along on that train trip and it's almost always completed by the time I arrive.... I love that. I can never get anything done when I'm trying to fly, though. Too stressful, and of course more crowded up against people which isn't fun either.

Maybe your trains are less crowded than ours :D
I often encounter pretty full trains in which it's no fun to travel. But yeah, when it's not too full it's less stressfull than flying in principle.

It's usually not bad on the trains here. Even when the normal seated areas are crowded, there's always a car for viewing with extra seats, and a car for selling food/eating, and you can go there, instead. So the density of people eases up a little, and even if you stay in the seat with people next to you, there's still MUCH more room than there is on an airplane.

Maybe that's really just different, then.
Our train seats only have a little more space than the plane ones. It is a little more, yes, but to me it doesn't make a huge difference. Most things I can do on the train I can also do on the plane, except the time I spend on there might be too short to do much. I find the most unpleasant things about going by plane the waiting at the airport and standing in lines and stuff.

For me the trouble with flying is the atmosphere. Everyone is so tense and tired and impatient and stressed that it's impossible to relax. On a train, mostly the people going are having fun, so the atmosphere is MUCH better.