Navigate to a CPT through two taxonomy queries??

Hi! I have a CPT named Products and two taxonomies, Brands and Product Categories. My client wants to start at a Brand page, displaying the Product Categories in the particular brand, then to click through to a page with all the Products under that Brand and Product Category.

Well, I have started this trek on the taxonomy-brands.php page and am trying to just query the product categories relevant to that brand, but for some reason, it is pulling ALL of the product categories. Any suggestions on a better way to accomplish this?

?php

$slug_brands = get_query_var( ‘term’ );
$term_brands = get_term_by( ‘slug’, $slug_brands, ‘brands’ );
$term_id_brands = $term_brands->term_id;
?>
<h1><?php echo $term_brands->name; ?></h1>
<p><?php echo $term_brands->description; ?></p>

<?php
$args=array(
‘post_type’ => ‘products’,
‘parent’ => 0,
‘tax_query’ => array(
array(
‘taxonomy’ => ‘brands’,
‘parent’ => $term_id_brands,
‘terms’ => $term_brands,
‘field’ => ‘slug’
)
)
);
$terms = get_terms( ‘product_categories’);
foreach($terms as $term) {
echo ‘
• ‘.$term->name.’

‘;
}?>

Thank you!