The Twitch App for Xbox has a new feature: you now have the ability to broadcast your Party Chat. To use this, enable the “Broadcast party chat” option in the Twitch app settings on Xbox. Members in your party will have the option to allow their audio to be heard by your stream. Should they decline, you’ll still be able to chat with them in your party, but they will not be heard on the broadcast. If you are the party leader, you also have the power to mute other members in your party even if they have opted-in. This new feature also includes party members that are on a Windows 10 PC.
This feature is great for those who stream directly from the Xbox One and play multiplayer games. Now, your viewers can hear who you are communicating with!
Source: Major Nelson