2 Apple Watches Pair with 1 iPhone.

Randy-12's comment is incorrect, and I don't know why the reference to the appleinsider.com article, since it says nothing about needing a Family Setup. "And now, it could not be easier than Apple's made it — once you've set everything up. From then on, switching between two or more Apple Watches is solely a case of taking one off and putting the other one on."

While this has always been the case, Apple installed faulty software in their servers during the last quarter of 2022, which prevented HomeKit devices from working with more than one Apple Watch. But at some point in January of 2023, the problem was corrected.

Hooray!

You’re quite welcome. I learned all this recently when I could no longer pair my two watches to one phone. After having a chat with Apple Support, I decided to do a bit of experimentation on my own. That’s how I discovered no one else can access those devices—Period.

Apparently, HomeKit has been the source of various security issues since it was created. I suspect they’re trying to address those. Now they’re trying to fix what they broke, without making it worse. Being a retired computer specialist myself, I wish them luck. As far as the rest of us are concerned… 🤷‍♀️

You can have different watches on one iPhone but only 1 watch can be active at once.

If you want more than one active at the same time use Family Setup

see https://appleinsider.com/inside/apple-watch/tips/how-to-sync-multiple-apple-watches-to-one-iphone

Yes, but…

Apple made a boo-boo in their server software recently, so now only one paired Apple Watch will work with HomeKit devices. The second Watch will show all the devices as unavailable.

And it gets worse… A second family member with their own iPhone, Watch and Apple ID cannot control the family HomeKit devices, either. No other Watch can. Only the one(s) previously connected will work.

No word yet on when Apple will have a fix for this. In the meantime, all those lucky kids who got Apple Watches for Christmas cannot control any devices in the house. Bummer!! The same goes for the wife or husband or anyone else in the family. Only the first Watch connected will work. The rest are out of luck.

Note: Apple Watches previously connected to the HomeKit devices will continue to work, unless a Watch is unpaired. After that, the Watch joins the rest of those that cannot connect.

It would appear Apple fixed this problem. Yay! You can once again have more than one Apple Watch running the same HomeKit devices.

Woo-hoo!