Red blood cell movement, deformation, and partitioning in small diverging microvessel bifurcations are simulated using a two-dimensional, flexible-particle model. For isolate red blood cell movement, while simulated red blood cell trajectories tend to follow background fluid streamlines, significant deviations from these streamlines can occur because of red blood cell migration towards vessel centerlines and red blood cell obstruction of downstream vessels. The net effect of these behaviors is explored in symmetric and asymmetric vessels to produce results comparable with experiment. In addition, preliminary results and insights are presented for multiple red blood cell motion in straight vessels and in bifurcations.