Thank you for your response and your patience is much appreciated.
If you want to simulate a single unit cell for both the structures, then you need to design a single lattice for both with some air gap. You cannot place two different lattice shapes on top of each other and simulate it. You need to convert the square lattice into hexagonal one and simulate your model. Remember that you need to use three pairs of coupled boundaries for hexagonal lattice rather than two pairs as for a general square lattice.
If you new to coupled boundaries and Floquest port then I suggest you to go through this free course from Ansys - Ansys HFSS Floquet Port - ANSYS Innovation Courses, Microstrip Patch Antenna Finite Array Creation Using Domain Decomposition Method in Ansys HFSS — Lesson 5 - ANSYS Innovation Courses.