Using backbone.js:
I have a top level ModelA that contains 2 attributes and 2 nested models, ModelB and ModelC. ModelB and ModelC each have 2 attributes as follows:<
There is backbone plugin Backbone-relational.js which provides one-to-one, one-to-many and many-to-one relations between models for Backbone.
I think this js will fulfill your needs. Vist BackboneRelational for more documentation.