2013 – Parent/Child Update on Workflow

I have a parent list (Contracts) with many child lists (Invoices, Companies, etc). The Parent:ID is a lookup on the child lists to relate them. I have figured out a way that when I update a people picker field on the parent it will update on the child, via workflow, however it only updates the first child.

How do I get it to cycle through and update all of the associated child items instead of stopping at the first one?