It is up to the applicant to decide how much priority to mention. If the landlord's two patents have the same content, it is good to mention the one with the earliest application date; If the contents are different and the landlord wants to protect them all, they should be mentioned together, but the priority request fee should be paid in two copies, and the PCT application documents should also include the contents of the first two application documents.
In addition, giving priority to the PCT application will not cause the earlier application to be considered as withdrawn, but only if the later application is also a domestic application, because the patent law stipulates that only one patent right can be granted to the same invention-creation.