[keycloak-user] Fwd: Users in Multiple Realms

Hello Please excuse me if this has been asked before (I'm sure it has), and I would be grateful if someone could point me to the right resources. I have 2 realms, REALM1 and REALM2, in my local instance of KC. I would like to validate and issue tokens for users who are members of a particular group in another realm on the same server. I.e., In REALM2, I've created a group e.g., REALM1-GROUP, and assigned users to this group, who I want to be validated in REALM1. How can I do this? Thanks in advance. Sam