$re = '/[^\S]*(\w*)(?:\s*)(?:\s*\([^()]*\)\S*)*/m';
$str = 'John (Juan, Jonathan, Jon, Jonny) James Doe (born on January 1, 1900) (Canada) James John (Juan, Jonathan, Jon, Jonny) James Doe (born on January 1, 1900) (Canada) James';
$subst = "$1*";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php