In this study we introduce a tool named Key Interaction Networks (KIN), a Python package that can construct a conservation-based RIN for a set of evolutionary related proteins. While there already exist a number of tools for analyzing protein interactions in multi-state structures , KIN provides the additional capability to analyze any group of related proteins by finding a common network of interactions that are conserved within the family. Specifically, using KIN, the RIN across the protein family can be projected onto a structure of interest and used to identify both conserved and variable interaction subnetworks throughout the family. Further, the RINs used can be determined directly from analysis of a single structure of each member (e.g., a crystal structure) or alternatively from an ensemble of structures (e.g. molecular dynamics trajectories of simulations performed on each member). To demonstrate the utility of KIN, we applied it to study 69 evolutionarily related class A β-lactamases, proteins that play a major role in bacterial resistance to β-lactam antibiotics . As we will showcase here, projecting conserved interactions onto a structure of interest allows characterization of the core interaction network across a family, which can in turn provide insight into functionally important residues and interactions as well as help to identify relevant residues that could be targeted for mutation. This makes KIN a useful tool both for advancing our understanding of the fundamental biochemistry of enzyme families as well as for protein engineering efforts.