When you see a forever-loader icon, it might be caused by a PHP error in your template file or template render callback. Please turn on the debug mode and see if there's any error in the log.
I think you should do some custom JS code to update the value of the children's first name based on value of their parent's first name. Unfortunately, we don't have that feature built-in.
Thanks for your comment. I think you can query users using the get_users() function. For each user in the loop, get his information via rwmb_meta() helper function (for custom fields).
Sorry for the delay. It's fixed in the latest version of MB Admin Columns and will be available in the next version of AIO (will be released in a few days).
