Atoms of element B (as anions) form hexagonal close packing (hcp) lattice and atoms of element A (as cations) occupy 2/3rd of tetrahedral voids. If atoms of element B (as anions of same charge as hcp lattice) forms cubic close packing (ccp) and atoms of element A (as cations) occupy octahedral voids, then,

Total number of voids unoccupied per unit-cell must be same in both crystal structures.

Total number of tetrahedral voids occupied in hcp is same as that of octahedral voids occupied in ccp.

Radii of cations of element A is same in both the crystal structures.

Average oxidation state of metal ion is different in hcp and ccp.