Dead and buried, but where?

I don't really talk about religion on here, save that my husband M is Catholic and I'm not (slightly ambiguous sorry) I'm an atheist and its not a problem for us.
We were at a wedding reception for M's Aunt on the weekend, and I was chatting to his cousin Lachlan and his girlfriend Jess. We ended up having one of those bizarre all around the place conversations where I ended up telling them an anecdote about discussing burial plots with M's grandparents (also his). I've grown up with only one Grandmother and her sister, my Great Aunt, and as a pair they're the closest thing to Grandparents I've ever known, its been like having two grannies. On the flipside, M has had four grandparents his whole life, and I've gotten to know them too. His father's parents were the ones we discussed burial plots with, they're very easy going and we got there in a very organic way; I didn't just come out and start talking about death and funerals. M's grandfather is also a twin, and I just couldn't resist asking them both about their viewpoints on who you get buried with. I imagine as a twin he feels a strong connection to his sister, but she's got a (deceased) husband of her own buried in another town, and he's got a lovely wife, and they seem very much in love and that they would want to spend eternity next to each other. So how do people reconcile where they're buried? My family doesn't really have family plots or anything that I know of. Mum's always said she wants to be cremated and Dad wants to be buried as far as I know, so I've never erally taken the cue from them.
So I was discussing this conversation with Lachlan and Jess, and it brought me to another topic I've always pondered upon, being the afterlife.
LOL no I don't mean in general, or something I muse about terribly often, but the one thing I've always been curious about, if when people have multiple partners, which ties into the burial plot thing too.
My maternal grandfather died when he was 47, so technically my grandmother has been a widow longer than she was even married to him for. He (I assume) is buried in the country town they lived in and he grew up in. But does that mean she will be buried there? And what would happen if she had met someone else after that? My mother was only 9 when he died, and in modern society my grandmother probably would have re-married. Her children were youngish, she had half her life still ahead of her! Which brings me to the afterlife part, if you DO re-marry, who do you spend your afterlife with?
I've always particularly wondered this about young widows/widowers. Say people that become widowed in their twenties, they're probably going to go on to love someone else just as passionately as they did their first husband. (for tidiness I'm going to stick to married couples, not life partners who I'm sure have the same dilemmas).
So we were pondering this point also, Lachlan, Jess and I (hey I said it was organic! It wasn't weird to be discussing this at a wedding until right at the end when they got that glassy-eyed look). So we're chatting, and a woman was getting a drink from the bar next to where we were standing, and she went onto say "you spend the afterlife with the person you like the most" if you have multiple life partners. Which I think beggers the question, what if YOUR most-liked-person, doesn't pick YOU as their most-liked-person???
She didn't think it mattered, they'd never know and that in their afterlife you don't care about any of that either. She actually took it as a sign that she was meant to hear our conversation, I think so she could enlighten us. I don't know about the accuracy of that, but it's certainly been food for thought since.