Steam library sharing question

[D1craig]

I just bought baldurs gate 3 on g2a games and went through all the steps it wanted me to go through to get it. At the last step I noticed it was giving me an account to log into to play the game. I didn't realise you could sell or buy steam accounts so never even realised it said account on the title of the purchase or I did realise but thought nothing of it. They wont refund me because i have done almost everything but logged into the account.

So the question. Can I do the family sharing thing with that account and my own and then never log into that account again? And will it work forever with that game?