wp_get_term_taxonomy_parent_id( int $term_id, string $taxonomy )

Source

File: wp-includes/taxonomy.php

function wp_get_term_taxonomy_parent_id( $term_id, $taxonomy ) {
	$term = get_term( $term_id, $taxonomy );
	if ( ! $term || is_wp_error( $term ) ) {
		return false;
	}
	return (int) $term->parent;
}