Drupal Example of Ajax on Field group multiple using hook_form_alter
This CodeLet let you konw how to implement ajax on field group multiple module.
"fgm_node_YOURNODE_form_group_YOURGROUPNAME" where "YOURNODE" will be the name of your content type and "YOURGROUPNAME" will be the name of your field group,
Given example is for text field, ajax call on blur event.