Share tokens between Two Clients in Same Realm

Hi!

We have the following scenario. We have two clients in one REALM, client A and client B in REALM C. Now, a user opens a session in client A and we provide a link that redirects to client B. We want to achieve the following:

→ Client B can use the same token as client A and therefore no need to enter log in credentials again or
→ Client B claims an own token but entering the log in credentials must be avoided

I am happy about any advise. Thanks in advance!