Ward owners (that aren't grandfathered) can hold a maximum of 9 total houses per account or 8 FC houses per account. So keep in mind that even though all 7-8 players are the same real person, SE considers ward owners to be 7-8 players, as they pay 7-8 subscriptions.

Ward owners have reported themselves out of curiosity, and been told that it breaks no rules. Is ward ownership fair? Yes, because anyone who wants to spend 400-700 million gil and $1500 per year in account subscriptions can do it. Is ward ownership considerate? Perhaps not, but the simple fact that it's possible shows that the average player is not motivated to buy the houses that the ward owners are selecting.

SE did what they were going to do against multiple house owners when they brought personal housing from 8 per world per account to 1. It seems unlikely they will make the same change with FC housing, after so much time. It is possible they will limit FC houses to one per account in the future, but if and when that happens, it is almost certain that any account already in possession of multiple FC houses will be allowed to keep them.