Data Cloud Related list for Account object from External Data

Hi , I have created 2 data streams in Salesforce data cloud - 

1. for Accounts from Salesforce Account object with External_ID__c as custom field.

2. Another for Sales Orders from Snow flake with customer_number__c. 

So both streams and their Data lake objects will have matching data. If I want to show Sales Orders related list in Salesforce, what all should I be doing? In the demos that i have seen, they are adding some Guest data, mapping it to individual object, that results into Unified Individual. Since my use case is Account related, this should result into Unified Account, I assume. But I really don't want to create another stream in Snow flake as it may simply duplicate Salesforce Account data. 

Am I missing any specific setup? or its not possible without duplicate Account Object in snowflake?

Thanks,

Sreekanth

#Data Management

#Data Cloud