If the passengers have different PNR's in the first place, that's not an issue. This issue is known to happen when they are on the same PNR, where the industry assumption is that a POS (passenger of size) is occupying 2 seats. Have highlighted this in my post above. The only 'remedy' is to have slightly different names (ie, repeated letter). This will pose a problem with some authorities and the airline FF program, but nothing that can't be fixed.