How to get term child?

I have three level categories in my WordPress site. It’s looks like:

Parent A
– Child A1
– – Child child A11
– – Child child A12
– Child A2
– – Child child A21
– – Child child A22
Parent B
– Child B1
– – Child child B11
– – Child child B12
– Child B2
– – Child child B11
– – Child child B12

I have a code:

<?php
        $termID = 3; // Parent A ID
        $taxonomyName = "products";
        $termchildren = get_term_children( $termID, $taxonomyName );
            echo'<div class="sub"> <div class="links">';
              foreach ($termchildren as $child) {
                  $term = get_term_by( 'id', $child, $taxonomyName );
                  echo'<a href="#">' . $term->name . '</a>';}
            echo'</div> </div>';?>

The result of the code is:

Child A1
Child child A11
Child child A12
Child A2
Child child A21
Child child A22

How to get only the Child without Child Child?