Obtener la lista de subcategorias pertenecientes a la misma categoria principal de la subcategoria actual en WordPress

jpb_list_categories.php

<?php

$term_id = (int) get_query_var('cat');
$current_term = get_term($term_id, 'category');
if ($current_term->parent !== 0) {
	$is_parent = FALSE;
	while (!$is_parent) {
		$current_term = get_term($current_term->parent, 'category');
		if ($current_term->parent == 0) {
			$is_parent = TRUE;
		}
	}
}

$term_childrens = (array) get_term_children($current_term->term_id, 'category');

foreach ($term_childrens as $term) {
	// do something
}