The factored state space approach (FSS) can be a powerful mathematical tool for the synthesis and analysis of non state space digital filters. In the following letter, this technique is used for the rederivation of some classes of low sensitivity filters described by a II-cascade two-pair structure. This method leads to a simplified synthesis algorithm (with applications to automated synthesis procedures for many classes of non state space digital filters) as well as a straightforward analysis of roundoff noise and norm scaling problems.