Using 2 Apple Watches setup from a single iPhone

[Saturn007]

Put it another way — one could buy a brand *new* Watch 9 today from Best Buy and pair it with an older iPhone that isn't running iOS 18!

Pretty sure that those Series 9 watches aren't on iOS 11! And that, therefore, a phone running iOS 18 isn't mandatory.

For sure, being careful and exploring requirements is essential. As I noted:

“Still, the underlying message is a good one — one definitely wants to check Watch and iPhone device, iOS compatibility whenever buying either.”​

​

As you and I both “discovered” or realized, the latest-released Watch will typically come with new iOS requirements that many old iPhones can't meet!

 

[Night Spring]

Put it another way — one could buy a brand *new* Watch 9 today from Best Buy and pair it with an older iPhone that isn't running iOS 18!

Pretty sure that those Series 9 watches aren't on iOS 11! And that, therefore, a phone running iOS 18 isn't mandatory.

You can still buy Watch 9? Ok, I didn't know that!

You are right that a new Watch 9 will likely come with watchOS 10, so that'll pair with iOS 17. But it won't pair with iOS 16.

So yes, matching Apple watches with the proper version of iOS is complicated. It's just simplest if both devices are on the latest OS.