How can I get notifications from two Android phones to one Android Wear watch?
There are a number of applications in the Play Store which are designed to allow a tablet to send/receive SMS/MMS via a connected phone. If you connect your watch-connected phone as the "tablet", you should at least be able to get notifications for some subset of events to show on your watch.

Caveat - I have used Tablet Talk for this purpose on a non-android wear watch, but not recently, and I don't recall all the limitations.