Your website citation confirms the 30-day information rule. I would strongly suggest obtaining the name of the occupant and estabish a policy for conducting a meet-and-greet session with the new occupant. The purpose would be to go over the house rules even in the presence of the shareholder. With good interviewing skills and good observation of body language, you may find alot about the occupant including relationship and perhaps surprise information that may be critical in finding out why the shareholder changes roommate so often.

Key items of the website citation are:

5. The tenant shall inform the landlord of the name of any occupant
within thirty days following the commencement of occupancy by such
person or within thirty days following a request by the landlord.
6. No occupant nor occupant's dependent child shall, without express
written permission of the landlord, acquire any right to continued
occupancy in the event that the tenant vacates the premises or acquire
any other rights of tenancy; provided that nothing in this section shall
be construed to reduce or impair any right or remedy otherwise available
to any person residing in any housing accommodation on the effective
date of this section which accrued prior to such date.

I would strongly suggest obtaining the name of the occupant and conduct a meet-and-greet session with the second occupant. In the meeting you may find, with a good art on interviewing, the relationship of this person to the tenant (shareholder) and also know the type of character this person is all about.