In reply to E.K..
Hi E.K.,
According to URA, the occupancy cap of six applies to all residing within the home, especially when owners rent out their private residences to unrelated persons who are not from the same family unit.
In your query, since your main unit is rented out to a family with children and a helper, that’s one family unit, while the studio is rented out to a couple who is unrelated to the family in the main unit.
As the main unit and studio are considered one single property, the occupancy cap of six applies to both. Hope this answers your question.
https://www.ura.gov.sg/Corporate/Media-Room/Forum-Replies/forum17-06
https://www.99.co/singapore/insider/dual-key-condo-units-property/