you cannot use items that belong to someone else, even someone in your family, without permission. If your family has a sort of understanding of permission, then fine, within the limits of that understanding.
On the other hand, those who are somech al shulchan avihem, perhaps don’t really have personal ownership, or very little of it.
Just the same most usually behave as if each is real owner, and respect each others ‘property’.
Even communists don’t consider the world hefker once something is distributed. (That’s a logical contradiction, but just add it to the list)