How to display full_name of user instead of user_name in listview for created_by field?

Hi,
I’m using SuiteCRM Version 7.9.2 Sugar Version 6.5.24 (Build 509). I need to show created_by and modified_by_name in listview for my custom module. When I try to display created_by and modified_by_name in listview using studio, instead of displaying full_name of user (according to the format set in the user settings), it always displays user_name for both of the values.

Can anyone help me showing full name for created_by and modified_by_name fields?

Here is the definition of both fields in listviewdefs.php

‘CREATED_BY_NAME’ =>
array (
‘type’ => ‘relate’,
‘link’ => true,
‘label’ => ‘LBL_CREATED’,
‘id’ => ‘CREATED_BY’,
‘width’ => ‘10%’,
‘default’ => true,
),
‘MODIFIED_BY_NAME’ =>
array (
‘type’ => ‘relate’,
‘link’ => true,
‘label’ => ‘LBL_MODIFIED_NAME’,
‘id’ => ‘MODIFIED_USER_ID’,
‘width’ => ‘10%’,
‘default’ => true,
),

Any help would be great.

Thank you