In this example, Product belongsTo Media and Category hasMany Product Media > Product > Category Product know mediaId Product know categoryId

nestedInclude.js

Category.findByPk(req.params.id, { 
  include: [
      {
        model: Product, as: 'products', include: 
          [
            {model: Media, as: 'image'}
          ]
      }
    ]
 })