Well obviously the legal team has nothing better to do than peer through your webcam to check that ONLY you are playing your account, and as soon as they so much as smell (how?) another potential user in the room as you they switch their surveillance to you to make sure only your hands are on the mouse/keyboard. (This is an obvious joke.)
The real answer is more than likely no, and even if it was how would they know and enforce it and why bother?
Who can tell. If you care about your account, just buy the family member in question a personal copy from the spring sale when it's as cheap as it gets.
Selling, Trading, and Sharing Game Accounts: The act of selling, trading, or sharing your ESO account is a violation of our Terms of Service. As such, we also do not allow discussion about selling, trading, or sharing game accounts on our forums.
If you have any further questions regarding our ToS, please feel free to submit a support ticket here: https://beth.games/2ZbRFOy