@hreddy I am not sure whether you had a look already this doc.

https://docs.servicenow.com/bundle/vancouver-it-operations-management/page/product/discovery/concept...

The relationship getting created based on a business rule not by discovery pattern. The business rule logic explained on that article above

Also if you face any issue in that this kb article also would help

https://support.servicenow.com/kb?id=kb_article_view&sysparm_article=KB0683837