gistfile1.php

<?php
/*
Plugin Name: Profile Builder Custom Page Title on Single User
Plugin URI: http://cozmoslabs.com
Description: Filter wp_title on the Single User Listing
Author: Cristian Antohe
Version: 1.0
Author URI: http://cozmoslabs.com
*/

add_filter( 'wp_title', 'wppb_custom_page_title', 10, 3 );

function wppb_custom_page_title($title, $sep, $seplocation){
	
	$singleUserListing = false;      

	if (isset($_GET['userID'])){
			$singleUserListing = true;
			$userID = $_GET['userID'];
			$user = get_user_by('id', $userID);
			$title = $user->first_name . ' ' . $user->last_name . ' ';
			if ($title == '  ') { $title = $user->display_name . ' ';}
	}else{
			$userID = get_query_var( 'username' );
			if (!empty($userID)){
				$singleUserListing = true;
				if ( is_numeric($userID)){
					$user = get_user_by('id', $userID);
					$title = $user->first_name . ' ' . $user->last_name . ' ';
					if ($title == '  ') { $title = $user->display_name . ' ';}
					
				} else {
					$user = get_user_by('login', $userID);
					$title = $user->first_name . ' ' . $user->last_name . ' ';
					if ($title == '  ') { $title = $user->display_name . ' ';}
				}
			}
	}
	
	
	return $title;
}
?>