WordPress trying to query two custom types to get child from the parent

So I was finally able to find what I needed:

                $loop2 = new WP_Query([
                  'post_type' => 'service',
                  'numberposts' => -1,
                  'meta_key' => '_wpcf_belongs_service-category_id',
                  'toolset_relationships' => [
                    'role' => 'child',
                    'related_to' => $parent_id,
                    'relationship' => ['service-category', 'service']
                  ]
                ]);

https://wp-types.com/documentation/customizing-sites-using-php/displaying-child-posts/