SQL Server 2016 GROUP BY +通过JOIN只能获得不同的记录

We have two tables, one for users and one for records. Records have a reference number and link to a user by a FK. We want to get reference numbers from the records table where the same reference number was used for different users. Two users are the same user if they have the same last name and same date of birth. Two users are different users if either last name or DOB are different.We have two tables, one for users and one for r