Multibody parts are not supported in NC assemblies. You cannot assemble reference models with multibody parts in NC assemblies. The message area shows a prompt whenever you try to assemble such a part. In the NC assemblies, you can assemble a multibody part with the Merge by reference or the Inherited options only as a reference model. However, the part will show only one body after you inherit or merge it. In this process, no data is lost as the multiple bodies are converted into one body.