The growth of waves along the direction of motion of thin viscous liquid sheets is investigated when lateral waves are additionally present. Gas streams are considered to move at different relative velocities over the gas-liquid interfaces. A dispersion relation is derived using spatial growth of the longitudinal waves. Para-antisymmetric waves are shown to have significant growth rates in the presence of lateral wave motion at larger values of Weber number, gas-to-liquid density ratio, and relative velocity ratio. The presence of lateral wave motion does not affect the growth rates when gas Weber number exceeds 10. The droplet sizes, formed from the disintegration of the liquid sheets, are also determined from the longitudinal and lateral wave numbers. The distribution of droplet sizes is modeled and it is shown that the droplet sizes formed in the presence of lateral wave motion, are restricted over a smaller range of diameters as compared to the wider distribution obtained in the absence of the lateral wave modes.