Is it possible for two iPhones to track an air tag?

No. AirTags can be tied to only one AppleID. Tracking dogs or people is not recommended; remember AirTags are not real-time trackers and require bluetooth proximity connections. So if your dig runs away, it's great in Manhattan, not so much in Manhattan, KS.

No. AirTags are tied to a single Apple ID, as such can only be tracked by one user, though they can be tracked from any of the user's devices.

So if you have an extra iPod Touch or older iPad with your own Apple ID, it can be used to track the AirTag.

AirTags are designed for personal use, and do not at this time support sharing them or tracking them by more than one person.

An AirTag is associated with one Apple ID. Each individual person has her/his own, unique Apple ID. Therefore an AirTag shows up as one person’s item.

Glad your question was answered.

Enjoy your Apple gear!