Is there any way to connect an Air Tag to two different devices, like my iPhone and my wife's iPhone?

I would say it’s just down to a privacy issue, I understand you and your wife are in the same house but for example if it was possible to pair your keys to another persons Apple ID then they would technically be able to track you. The only solution is if Apple ever made a feature like “household” then maybe you could at least see members of your family plan items the same way we can see devices, we can only hope.

Hello Dakota, no sadly this is not an option. An individual AirTag can only be paired to one Apple ID and tracked by that Apple ID.

No.

There might be an awful way (sharing an Apple ID), but you absolutely should never consider doing that.