It appears for PC each account has to have their own game code so it seems its not available to share

see more info and make sense of how it may apply I don't do this via steam sorry but maybe it helps



http://store.steampowered.com/promotion/familysharing

Can all Steam games be shared with friends and family?

No, due to technical limitations, some Steam games may be unavailable for sharing. For example, titles that require an additional third-party key, account, or subscription in order to play cannot be shared between accounts.



https://help.elderscrollsonline.com/app/answers/detail/a_id/5729/kw/game code
Is it possible to buy one copy of the game and have two game accounts in the same user account?
Updated 09/29/2015 08:20 AM Published 02/19/2014 10:59 AM

No. There can only be one game code on any given account.

If you wish to play on two different accounts, you will need to set up two accounts with different account names and e-mail addresses. On PC/Mac, it is also required that you purchase two separate copies of the game.


https://help.elderscrollsonline.com/app/answers/detail/a_id/21649/kw/steam share

Can I buy multiple copies of ESO on Steam?
Updated 10/14/2016 10:01 AM Published 06/26/2014 09:32 AM

You can purchase more than one copy of The Elder Scrolls Online using the same Steam account. However, only one copy of the game can be linked to one Steam account. The "Purchase for myself" option will only be available for the first copy, and then it will be greyed out leaving only the "Purchase as gift" option available for the other copies.

Additionally, it is not possible to add multiple copies of the same game in the Steam cart.