Product family design (PFD) is one of the commonly adopted strategies of product realization in mass customization paradigm. Among the current product family modeling approaches, ontology based modeling has been identified as a promising approach. Previously, we have studied the feasibility of using a semantically annotated multi-facet product family ontology in performing product analysis and variant derivation in the PFD domain. However, the visualization aspects of the ontology are important to assist product designers and engineers to gain insights and benefit from the ever-increasing information from the ontology, e.g. dimension, assembly or configuration wise. From the previous literature, we observe that there are limited usage of visualization and interaction in PFD for tasks such as product analysis and variant derivation. The current hierarchy based representations are limited in displaying ontological relationships and tasks such as commonality analysis seldom make use of visualization to foster better understanding of component similarity. In this study, we report our efforts in assisting product family analysis and variant derivation through visualization and user interface (UI) which enables interactive PFD. Design considerations for our visualization and user interaction design are discussed. By using a multi-touch UI, we discuss on how our UI is able to enable users to better perform product analysis and variant derivation based on the aforementioned ontology in an interactive, intuitive and intelligent manner. We finally conclude this paper with some indications for future works.