It’s all about whose name is on the strata roll. It’s generally accepted that only one of a couple who are joint owners has to attend a general meeting to vote. And the attendee can’t nominate themselves for election to the committee – they need a letter of nomination from their co-owner.
Regarding multiple owners, this is usually done through a company structure in which case the company’s official nominee should be established in writing with the secretary, under Section 22 of the Act.
This only applies to general meetings – owners can’t vote at committee meetings unless they are on the committee and only one co-owner from each property can be on the committee.