Dual (<~ 10 kpc separation) and binary (<~ 10 pc separation) supermassive black holes (SMBHs) are formed during the merger of two galaxies. Their formation and evolution is controlled by interactions with their environment and, at close separations, the emission of gravitational waves. Accordingly, the occupation fraction of dual SMBHs in galaxy merger products is central to our understanding of galaxy and SMBH evolution, and determining the rate of dual active galactic nuclei (AGN) in galaxy mergers will advance our understanding of merger-induced SMBH fueling and growth. The rate of gravitational wave-driven SMBH mergers is critical to the predictions for gravitational wave signals that will be detected by pulsar timing arrays (such as the North American Nanohertz Observatory for Gravitational Waves [NANOGrav]) and future space-based laser interferometers (LISA). A related prediction is that AGN can appear offset significantly from the host galaxy due to gravitational wave "kicks" during the merger of an asymmetric SMBH binary. We review the current status and likely 2030s landscape for SMBH pairs and binaries, with a particular focus on the role that the ngVLA can play. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. The NANOGrav project receives support from NSF Physics Frontier Center award number 1430284. ?