When two or more Users need to stream content to the same Twitch account (but not necessarily at the same time), the safest way to do this is to utilise an accounts Permissions feature, "People who can stream to your channel", rather than sharing the Primary Stream Key (not-recommended) and/or account information to 'authorised' parties. Notwithstanding general security issues, using the "People who can stream to your channel" option makes account sharing redundant.
Important: the feature/functionality described below is not to be confused with simultaneous streaming, i.e. multiple people streaming to the same channel at the same time. 'Simulcasting' is specifically catered to by using the new Guest Star feature (https://dashboard.twitch.tv/u/[account-name]/guest-star), or by setting up individual Artist roles in Roles Manager (https://dashboard.twitch.tv/u/[account-name]/community/roles).
Note: People who can stream to your channel does not grant general account access, it only permits direct streaming. To manage an account check the various 'moderating' or 'editorial' setting or options in Roles Manager (found under Community).
Streaming Invite
To set up another person so they can stream to the same Twitch account/channel; in the Creator Dashboard click Settings and then Stream. Scroll down the page to the Permissions section. Here, mouse over the "People who can stream to your channel" area to highlight then click. This displays the People who can stream to your channel panel (when doing this Twitch highlights the Channel menu option).
Important: Permissions may only be available to qualifying accounts (https://dashboard.twitch.tv/u/[account-name]/analytics/achievements).
In Twitch Creator Dashboard access the Stream options under Settings
In the Enter an email address input field type the email address of someone who to be granted access to direct streaming and click Send Invite. Twitch will send an invite with a unique stream key (invited emails are then listed below the input box).
Scroll down to Permissions and click People who can stream to your channel option to send an invite (and to list/manage access).
Accepting Invite
On receiving the invite the unique stream key then needs to be copy/pasted into the stream settings of the app used to livecast to Twitch. How this is done differs depending on the app and the way account access is actioned, for example, in OBS Studio the stream key is dropped into the Stream options under Settings alongside the ingest URL rtmp://live.twitch.tv/app/;
Service - Custom...
Server - rtmp://live.twitch.tv/app/
Stream Key - [key from email invite]
Note: in OBS Studio the Service parameter must to be set to Custom... else Twitch login details will be requested - OBS assumes the User is streaming to an account they own or have access to. To stream to another account without login details (recommended action) OBS must be forced to stream directly to the default ingest for Twitch, which then correctly routes the incoming data where it needs to be.
Once done, upon going live, streamed data will be sent to the Channel associated with the invite, further being managed by whomever has account or editorial access.
The email invite sent from Twitch will include a unique stream ID associated with the account
In the streaming app of choice the unique key sent from Twitch needs to be dropped in place - where this is done may differ app to app
