Relationships is one of the features, to me that feels like Apple ended up building functionality on top of years after the feature was released, but since it was useless for so long nobody ever uses it.
Did you know not only could you specify your relationships, but other people's relationship's as well? I'm not sure if Siri lets you contact people this way ("Call John's mom"), but I wouldn't be surprised if a hidden update to Siri enabled this feature as well.
FWIW it's been in the MAC address book since the original OS X (jag-wire?)
It's a hard problem. Has anyone really solved it well that offers the use cases our current smart phones/computers have?
https://hbr.org/2018/09/design-thinking-is-fundamentally-con...
"so-and-so is my wife" => it will update that contact's info (and yours). Then later you can say "text my wife I'm on my way home" and it will.
"call me Mister Smith" => it will update your contact's nickname and use that to address you
"Take me home" (or to work/etc.) => it will bring up directions in apple maps to the "home" address on your contact
All devices need a universal undo so you can change something and easily undo if you get it wrong or you just preferred the old setting.
For security you could prompt after a while to make the new settings permanent and delete the snapshot.
At the very least, the emergency contact info should be stupid simple to find (I'd say top level in Settings). This isn't an "advanced" feature, it's a fairly vital and basic feature of a cell phone. Family relationship specification should be simpler too.