The point-defect coupling under the tight-binding approximation is introduced to describe the behavior of dispersion relations of the guided modes in a single photonic crystal waveguide PCW and two coupled identical PCWs. The cross-coupling coefficient of a point defect in one PCW to the nearest-neighboring NN defect in the other PCW causes the split of the dispersion curves, whereas the cross-coupling coefficient to the next-NN defects causes a sinusoidal modulation to the dispersion curves. Furthermore, the sign of determines the parities of the fundamental guided modes, which can be either even or odd, and the inequality 2 is the criterion for the crossing of split dispersion curves. The model developed in this work allows for deriving the coupled-mode equations and the coupling length.