An assembly process plan for a given product provides the sequence of assembly operations, their times as well as the required tools and fixtures for each operation. Much research has been done on automating and optimizing assembly sequence generation as the most important part of an assembly process plan. A novel method for generating the assembly sequence of a given product based on available assembly sequence data of similar products is presented. The proposed method uses a binary tree form to represent the assembly sequences of an existing family of products. A Genetic Algorithm is employed to find the consensus tree that represents the set of all assembly sequence trees with minimum total dissimilarity distance. This is similar to defining Generic Bill-of-Material. The generated consensus tree serves as a master assembly sequence for the product family. The assembly sequence for a new product variant that falls within, or significantly overlaps with, the scope of the considered family of products can be directly extracted from the derived master assembly sequence tree. The developed method is demonstrated using a family of three control valves. This novel method greatly simplifies and enhances automatic assembly sequence generation and minimizes subsequent modifications, hence, reduces assembly planning cost and improves productivity.