[TheOtherHobbes]

You probably don't need to be polyamorous to do this.

But it's an expensive option given all the paperwork (and taxes) you'd have to file at least once a year.

In the UK, you'd probably be better off incorporating as a trust - perhaps even a charitable trust, if you can find a good enough cover story.

And you may think you're joking, but a lot of families set up financial trusts for their assets for exactly these reasons.

It would be unusual for a trust to include non-married partners, but I don't see why it would be impossible.

[honestcoyote]

I honestly wasn't joking at all. It's something I've thought of off-and-on over the years.

I could see how a trust would be better, though, in the US at least, I think a corp / LLC might be more flexible. And here, especially if the corp is formed in a few rules state like Nevada or Delaware, the paperwork isn't too terrible for small organizations.

[mirimir]

How about a mix of marriage and adoption?

Just assemble a cross-linked family. Write powers of attorney, medical directives, wills, and so on.