I’m not sure what the problem is. Does it matter which part-owner turns up? So long as both aren’t there and holding up the meeting by disagreeing with each other, why do you care which of these two owners is at the meeting?
This may be my ignorance – in a jointly-held property, do the joint owners have to nominate which of the joint owners will attend meetings and vote? That doesn’t happen in my scheme. We accept attendance by any one owner of any property. Spouses frequently decide on the day of the meeting who can attend based on work commitments.