Programmatically accessing a field group relationship
I couldn't find one in the module anywhere but I cobbled this together and it seems to work ok:

function field_get_field_group($field) {
  $group_info = field_group_read_groups(array('entity_type' =&gt; $field['entity_type'], 'bundle' =&gt; $field['bundle']));
  foreach ($group_info[$field['entity_type']][$field['bundle']]['form'] as $group) {
    if (in_array($field['field_name'], $group-&gt;children)) {
      return $group;
    }
  }
  return FALSE;
}


Usage:

$field = field_info_instance('node', 'field_image', 'article');

if ($field_group = field_get_field_group($field)) {
  $group_name = $field_group-&gt;group_name;
  // etc...
}


You'll probably want to add some error checking ;)