$re = '/{{Template1(?:[^{}]*?(?:{{[^}]+?}}))+(?:}+)*/sm';
$str = '...
abas asdn asf asfs af{{Template1|a = Name surname|b = jhsdf sdf|c = {{Template2}}|d = |e = [[f]] and [[g]]|h = asd asdasfgasgasg asgas jygh trdx dftf xcth|i = 73|j = {{Template2|abc|123}}|j = {{Template3|aa=kkk|bb={{Template4|cc=uu}}}}}}asd wetd gdsgwew g{{OtherTemplate|sdf 213}}...';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
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