RAML override required field or

I'd like to change the required field for a type that I am inheriting in another type. Is it possible to override that value or abstract it somehow? In the example below, I'd like to override the required field for Passenger.firstName:

 Description: "Passenger"
 type: object
    properties:
      firstName:
        type: string
        example: Sansa
        description: first name
      lastName:
        type: string
        example: Stark
        description: last name
      gender:
        .
        .
        . 
        .
    passengers:
      description: passenger details
      required: false
      type: array
      items:
        type: !include passenger.raml
          properties:
              firstName:
                required: false

My goal is to not have to create different types when I want to implement the Passenger object.