Understanding and application

To whom does the final pronoun هِمَا in إِلَّا بِإِذْنِهِمَا refer?

Respectful Gatherings, Goodwill, Charity, and Valuing Time (Hadith 169–176)

• Only the third person who wants to sit
• The two people between whom the seat lies
• Everyone attending the gathering
• The organizer of the gathering