Based on the Stokes parameters, the complex Stokes scalar fields and the Fresnel diffraction integral method, the expressions for the composite Stokes singularities versus amplitude ratio η in two coherently and incoherently superimposed paraxial monochromatic vector optical beams were derived. The properties of composite Stokes singularities in coherently and incoherently superimposed vector optical beams with amplitude ratio propagating in free space were investigated, and the degree of polarization versus the amplitude ratio is analyzed. It is found that, during propagating in free space, the number, position and singularity index of composite Stokes singularities are affected by the amplitude ratio of two vector beams. In the coherent superposition the degree of polarization P=1. At the z=0 plane, when the amplitude ratio η≠1, singularity indices of C-points, S23 and S31 singularities may be reversed. The creation of S23 singularity with double singularity index may take place at the z>0 plane. In the incoherent superposition, the degree of polarization P is less than 1 and is variable with η, by varying the amplitude ratio η V-points may appear, which are unstable and split up into S23 singularities and C-points with handedness reversal. With a further increase of ηS23 singularities may annihilate. In addition， the sum of singularity indices of composite Stokes singularities is conserved in the process.