Atomic distributions of intercalated guest atoms into layered dichalcogenide have been simulated taking into account the interactions between the first and second nearest neighboring guest atoms in the triangular lattices stacked with 6 layers (lattice size 18 x 18 x 6) using a MonteCarlo method. With these distributions, the X-ray patterns of FexTiS2 with x = 0.25 having the 2 root 3a x 2a x 2c superlattice with the fractional site occupancy have been reproduced qualitatively by averaging the intensities for different patterns obtained by different random seeds.