I'm sorry, but the provided knowledge sources do not contain an example of adding a new relationship for Ory Keto using gRPC. However, they do contain examples using the REST API and the command-line interface (CLI). For more information on how to use gRPC with Ory Keto, you may want to refer to the [Ory Keto documentation](
https://www.ory.sh/docs/keto/).