Parallel mechanisms are increasingly being used as modular subsystem units in various robots and man-machine interfaces for their superior stiffness, payload-to-weight ratio and dynamic properties. This leads to series-parallel hybrid robotic systems which are difficult to model and control due to the presence of various closed loops. Most model based kinematic and dynamic modeling tools resolve loop closure constraints numerically and hence suffer from inefficiency and accuracy issues. Also, they do not exploit the modularity in robot design. In this paper, we present a modular and analytical approach towards kinematic and dynamic modeling of series-parallel hybrid robots. This approach has been implemented in a software framework called Hybrid Robot Dynamics (HyRoDyn) and its application is demonstrated with the help of a series-parallel hybrid humanoid robot recently developed at DFKI-RIC.