The widespread adoption of digital twins gave rise to emerging systems of interconnected digital twins, often dubbed aggregated or hierarchical digital twins. In such emerging systems, interoperability of digital twins is key in determining the capabilities and qualitative properties of the emerging system. In this paper, we report on a panel discussion that took place at the 2023 Annual Simulation Conference with four esteemed experts representing four distinct perspectives on the topic: strategic (why aggregated digital twins matter?), technical (how co-simulation supports a distributed set of concerns over multiple digital twins?), standardization (how standards enable interoperability?), and organizational (how organizations deal with digital twinning scenarios?). We report the panelists’ main arguments and synthesize them into a discussion. The main takeaway of the panel is that contrary to the state of affairs in digital twinning that limits interoperability to low levels, there is a clear need to reach higher levels of interoperability in digital twinning scenarios that necessitate a distributed approach. Moreover, there are emerging solutions to achieve these higher levels. To provide researchers with tangible leads, we distill challenges and success factors, and recommend future research directions in digital twin interoperability.