Yes to my sister's husband @BitcoinAbhi who's also my friend, if you consider him to be a kin.

My wife isn't at all interested, nor does she possess skill to learn the technology.

Yes, my brother knows everything about my stack, including the keys.

I haven't experimented with any fancy multisig setups or inheritance configurations yet. I'm still a noob in that regard.

I too. But I think it's not a big deal.