Get Account and Related Custom module data

Get Account and Related Custom module data

I have done a lot of research on this, and apologize if  this is a redundant question. But I want to be sure that what I have found is true... We have custom modules tied to Accounts, so for example we have a custom module called Employees.. I would like to open an Account by ID and get all related Employees..  From what I have been reading I cannot use the getRelatedRecords for this because Employees is a custom module. I also cannot use the ACCOUNTID that is automatically created on the employee record... So basically have to create a custom field that I reference when trying to open employees for a specific account? Hope that makes sense.