A request to establish an IM session is received. For example, a Session Initiation Protocol (SIP) INVITE message is received. The request is to an Address of Record (AoR) that has two or more associated communication endpoints on different IM systems. The request is forked to the two or more communication endpoints. An IM communication server, acting on behalf of a first communication endpoint, receives one of the forked requests. The forked request is automatically answered. For example, the IM communication server can automatically send a SIP 200 OK message. The answer causes the second forked request to be automatically canceled. The IM communication server sends a second request to the second communication endpoint to add the second communication endpoint to the IM session. This allows each communication endpoints to display a single instance of an AoR on the IM session.