There won't be any relationships.

You have to code it in with FKeys and Pkeys.

If you have Pkeys on Identities, then use this.

http://www.sqlservercentral.com/scripts/integrity/136833/

It will give you a rough guess how tables could possibly be related.

Dont go creating foreign keys willy-nilly.

If the script suggests FKeys, check the data in those columns, that they are as expected.

Then test the FKeys in QA with the application that runs on top of this DB.