This work deduces principles of bioinspired product architecture to effectively leverage biological function-sharing in engineering design. Function-sharing enables a single structure to perform multiple functions and can improve the performance characteristics of a system. The process of evolution via natural selection has led to the emergence of function-sharing adaptations in biological systems. However, the current practice of bioinspired function-sharing is largely limited to the solution-driven imitation of biological structures. This work aims to overcome such limitations by performing a function-based analysis of biological product architectures. First, a phylogenetic approach is used to select generalized case studies from the animal kingdom. Next, the product architectures of the selected case studies are then modeled using function modeling and analyzed by clustering the identified functions into modules. A function-based categorization of the sampled biological modules reveals the presence of four types of modules in the biological case studies. Analyzing the function-sharing scenarios associated with each type of biological module enables us to deduce four guidelines for bioinspired development and arrangement of function-sharing modules. Finally, a demonstration study applies the guidelines to the design of an inlet–outlet port for a washer–dryer system. The deduced guidelines can enable engineers to identify function-sharing scenarios in the early stages of product design and reduce the need to imitate biological structures for function-sharing.