Pivot table that has pivot

I have a these models; Child, Toy, Brand

Child M:N Toy, Toy M:N Brand

Here are my pivot tables;

child_toy_pivot | toy_brand_pivot   
------------------------------------------------
id              | toy_id
child_id        | brand_id
toy_id          |

Before giving the child a toy, the system must check if the child already owns that toy that has the same brand. So rather than making a pivot table with 3 foreign keys in it, I just made another pivot table

unnamed_pivot       | 
--------------------|
child_toy_id        | 
brand_id            | 

I would like to know how could I apply this in eloquent? How could I create a new record in it?