Custom Groups and Shared Portfolios

Are custom groups viewable in shared portfolios? I have a personal portfolio which I have set up custom groups for. I notice my other portfolios also have the option to report by these same custom groups. So I understand that custom groups are not set up on a portfolio by portfolio basis but instead on a user basis.

However, one of my portfolios is shared amongst a group of investors. When they login, will they have the option to sort the shared portfolio by the custom groups as well? This would effectively give them visibility of which investments in the shared portfolio I also own myself which would not be ideal.