header.php

<?php 

// Get our current authors info
$author = get_queried_object();

// Contains the username which should match the Gravatar account URL.
$gravatar_login = $author->data->user_login;

// Get all the Coauthor Plus data
$coauthor = array_shift( get_coauthors() ); 

// Get the authors name and store it in a variable
$author_name = $coauthor->display_name;

// Contain our coauthor email into a variable. This may be overwritten when account is linked
$avatar_email = $coauthor->user_email;

// Setup some new variables or override some when an author is linked.
if ( ! empty( $author->linked_account ) ) {
    // We need the ID of the linked author so we can get their posts.
	$linked_author = get_user_by( 'slug', $author->linked_account );

	// Return the linked authors name
	$author_name = $linked_author->display_name;
	
	// When an account is linked, we want to add this email into mix to see if we return gravatar data
	$gravatar_login = $linked_author->user_login;

	// Set linked account email as the gravatar email
	$avatar_email = $linked_author->user_email;
}
make_get_header();