Custom author rewrite urls for WordPress

functions.php

<?php

// Custom author URI structure even if the site
// is configured to use a custom structure, ie: /my-prefix/%postname%/
add_filter('init', function () {
    global $wp_rewrite;

    $wp_rewrite->author_structure = '/' . $wp_rewrite->author_base. '/%author%';
    // Only uncomment the flush_rules() method call if things are not working.
    // After the rules are flushed (refresh page), this can be commented out again.
    // $wp_rewrite->flush_rules();
});

You can even set a custom author_base, ie:

<?php
// /member/%author%
$wp_rewrite->author_base  = 'member';