Service Tickets interlinked

Hi,

There are two service tickets in the SAP CRM system, they are interlinked and there is a need to delete one of them (the second one created), as they are linked in the documet flow I cannot delete it without first deleting the preceding ST.

What would cause two service to become incindiary/linked in such a way, is there any way to remove this link and to remove/delete the service ticket.

Any help would be gretaly appreciated