What is the pass Id of current record to Salesforce Apex Controller?

I'm working on a Visualforce Email Template which will be sent from the parent Loan (LLC_BI__Loan__c) record in Salesforce, and I'm trying to include fields from the child Entity Involvement (LLC_BI__Legal_Entities__c) record(s).

I'm attempting to pass the Loan record ID into the Controller using the ApexPages.StandardSetController method, but I think it may be failing due to the fact that the Visualforce component is being used in the email template and not on a record page.

I'm unable to pass the correct parent (Loan) Id to get the correct child records. Can anyone see where I may be going wrong ?

Thank you in advance.

Component:

    <apex:component controller="BorrowerRecordsFromLoans" access="global">
<apex:attribute name="currentRecordId" description="" assignTo="{!loanId}" type="Id"/>
    <apex:dataTable value="{!borrowerList}" var="borrower">
        <apex:column >
                <apex:facet name="header">Borrower Name</apex:facet>
            {!borrower.LLC_BI__Account__r.Name}
        </apex:column>
    </apex:dataTable>
</apex:component>

Controller:

public class BorrowersOnLoans { 

public Id loanId {get;set;}

private final LLC_BI__Loan__c loan;

public BorrowersOnLoans (ApexPages.StandardSetController controller) {
        loan = (LLC_BI__Loan__c) controller.getRecord();
    }

    public List<LLC_BI__Legal_Entities__c> getrelatedBorrowers()
    {
        List <LLC_BI__Legal_Entities__c> conList = New List<LLC_BI__Legal_Entities__c>();

        for(LLC_BI__Loan__c ln:

        [SELECT id,name, (SELECT id, LLC_BI__Borrower_Type__c, LLC_BI__Account__r.Name FROM LLC_BI__Legal_Entities__r) FROM LLC_BI__Loan__c WHERE id = :loanId])
        {
           for(LLC_BI__Legal_Entities__c con:ln.LLC_BI__Legal_Entities__r)
               conList.add(con);
        }

        return conList;
    }
}