class Organization
  include Mongoid::Document

  field :name
  validates_presence_of :name

  has_many :members
end

class Member
  include Mongoid::Document

  belongs_to :organization
  
  field :name
  field :email
  validates_presence_of :organization, :name, :email
end

org = Organization.create!(name: 'Pipewise')
m = Member.new(organization: org, email: 'admin@pipewise.com')
m.save(validate: false) # <= returns true as expected
m.errors.present? # <= returns true, while expected false