Is it possible to connect two headsets to the watch and then listen by two people ?
Very possible.
Many small portable headphone amps/dacs can do this, I use a Creative E5 and have tested with my 5x+ It's small and has very long battery life, the only downside is the headphones need to be wired to the dac, but it has dual output so both headphone jacks are amplified no spliter or anything needed. If you are using it for camping, rowing, bike trainer, or other semi stationary activity this could work. Personally I use this approach for sporting events from a radio wired to the dac or BT from my phone to the dac (Think Formula 1 racing) so that my and my GF can both listen. It works the exact same from the Fenix, just not sure what scenario it would be valuable in.
So you connect your watch to the dac and connect two wired headphones to your dac and go running with your girlfriend while dac is stringed to wires between you and shaking along the run? :D I think what he asked was can watch connect to two wireless headphones and transmit music both at the same time. So I think that's not very possible but yours is a viable solution while you're sitting.
You saw that I clearly identified my solution was only for stationary activities and it had a limited use case, right? You are assuming a lot, do you know if he wants to do it while running? Maybe he wants to climb a mountain and watch sunset with his GF and listen to music.
