When a php file is processed via nginx & php-fpm, who owns the process ? NGINX or PHP-FPM?

My PHP-FPM runs as user www-data and NGINX server runs as user nginx. I am trying to browse a file that is written in php e.g example.com/index.php.

So when php-fpm executes the index.php in server who owns the process nginx or php-fpm ?

I had read somewhere nginx passes the php file to fast-cgi server, fast-cgi server runs the php file and generates the html content and send back to NGINX and NGINX again send back to browser.

So according me as nginx is the parent process of fast-cgi process, nginx should be the owner of the process. Please correct me if I am wrong.