Probably technically, but I can almost guarantee you they quite literally couldn't care less about two brothers sharing an account. They're more worried about large groups sharing an account.

[–] Deello@lemm.ee 2 points 5 months ago

Over the years I have heard stories where Valve closes an account after the owners passing. This is usually because the poster said they had trouble with something and explained that the original owner passed. Valve then responds by closing the account and ignoring the issue.

With that said I don't think large groups of people can effectively share a library/account because only one person can play at a time. Small groups like spouses, parents, siblings or a small friend group is doable because it is easier to coordinate who is gonna use the account at any given time. This is especially true if they live together.

With the Deck, I have issues where I boot up a game on my living room PC and my Deck closes it's game making me lose progress on the Deck. Imagine that multiplied 20x. Getting kicked mid match, losing that boss fight, lose your high score, getting left on cliffhanger mid cutscene. The throw your controller rage stuff.