I just needed to include the ‘parent’ in the schema. Thanks.
First of all, there is no such thing as optional: false since any key in a simple schema is required unless otherwise declared optional: true
Also, what is the schema definition of the common parent? That can significantly change how a field is validated. You should take a look at the section about objects and arrays on this page https://github.com/aldeed/meteor-simple-schema#optional