(2) The authority to pass a by-law under section 34, subsection 38 (1) or section 41 does not include the authority to pass a by-law that has the effect of distinguishing between persons who are related and persons who are unrelated in respect of the occupancy or use of a building or structure or a part of a building or structure, including the occupancy or use as a single housekeeping unit. 1994, c. 2, s. 43.