With Corresponding Entity References module is possible. We can handle bidirectional relationships, and that's very practical!
For example: we can relate a product "iphone" an accessory "case" from any of the two nodes. This will improve the usability of managing your Drupal considerably.
We create reference fields on both sides, then simply create the relationship between the two fields in the module configuration.
Now our fields are in sync and automatically updated.
Download module: Corresponding Entity References