From your Hopper, go to:
Settings >> Internet >> Advanced (Tab) >> Bridging >> Set Bridging to "ON"
[?] Bridging: Allow Joeys to access features such as Pandora, Netflix or On Demand by sharing your Hopper's Internet connection. Turn bridging on to share your Hopper's Internet connection with Joeys throughout your home.
I don't know if this will allow you to share YouTube or not, but it will certainly allow the Joeys to access Netflix.
After you make the change, I recommend restarting your Hopper and all of your Joeys. I hope you see this message and it helps and makes the use of your Joeys much better for you!