Entity reference count in a parent node
You can either use Views and Aggregation to Sum the number of references to show on a list.

But, I recommend using the Computed Field module to write some PHP code that is run on save to store an integer value that is the count of references. This value can be cached by drupal and used within Views and other modules.


  Computed Field is a very powerful field module that lets you add a
  custom "computed fields" to your content types. These computed fields
  are populated with values that you define via PHP code. You may draw
  on anything available to Drupal, including other fields, the current
  user, database tables, you name it. (Feeling the power yet? :) ) You
  can also choose whether to store your computed field values in the
  database with other content fields, or have them "calculated" on the
  fly during node views. (Although you should note that Views use
  requires database stored values.) This field is literally the Swiss
  Army knife of fields. So start cooking up your PHP based values!