Nested forms...

class Book < ActiveRecord::Base
  has_one :author
  has_many :pages

  accepts_nested_attributes_for :author, :pages
end

accepts_nested_attributes_for :author, 
  :reject_if => proc { |attributes| attributes['name'].blank? }

OR TRY THIS:

class Person < ActiveRecord::Base

  validates_presence_of :name

  has_many :children, :class_name => 'Person'
  accepts_nested_attributes_for :children, :allow_destroy => true
    # can also be used on has_one etc.. associations

end

<% form_for @person do |person_form| %>

  <%= person_form.label :name %>
  <%= person_form.text_field :name %>

  <% person_form.fields_for :children do |child_form| %>

    <%= child_form.label :name %>
    <%= child_form.text_field :name %>

    <% unless child_form.object.new_record? %>
      <%= child_form.check_box '_delete' %>
      <%= child_form.label '_delete', 'Remove' %>
    <% end %>

  <% end %>

  <%= submit_tag %>
<% end %>