Hi @cynthia_madden ...
I *think* only one person can be the "author" or "owner" of a shared piece of content in Commons. Someone else had a similar question recently, and I had suggested maybe setting up a generic Canvas account that is not tied to a specific person. That way, this account could be used by more than one person just for the purpose of sharing specific content. (I know that sharing user accounts isn't a great practice, but it might be a work-around for this situation.) Then, people could log in with that account to update the content as needed.
Again...maybe not the most ideal solution, but thought I'd share my $0.02 ... for what it's worth.