single.php

// Remove Genesis Author Box and load our own
remove_action( 'genesis_after_post', 'genesis_do_author_box_single' );
add_action( 'genesis_after_post', 'be_author_box' );

/**
 * Load Author Boxes
 *
 * @author Bill Erickson
 * @link http://www.billerickson.net/wordpress-post-multiple-authors/
 */
function be_author_box() {

	if( !is_single() )
		return;

	if( function_exists( 'get_coauthors' ) ) {
		
		$authors = get_coauthors();
		foreach( $authors as $author )
			be_do_author_box( $author->data->ID );
			
	} else {
		be_do_author_box( get_the_author_ID() );	
	}
}

/**
 * Display Author Box
 * Modified from Genesis to use an ID
 *
 * @author Bill Erickson
 * @link http://www.billerickson.net/wordpress-post-multiple-authors/
 */
function be_do_author_box( $id = false ) {

	if( ! $id ) 
		return;
		
	$authordata    = get_userdata( $id );
	$gravatar_size = apply_filters( 'genesis_author_box_gravatar_size', 70, $context );
	$gravatar      = get_avatar( get_the_author_meta( 'email', $id ), $gravatar_size );
	$title         = apply_filters( 'genesis_author_box_title', sprintf( '<strong>%s %s</strong>', __( 'About', 'genesis' ), get_the_author_meta( 'display_name', $id ) ), $context );
	$description   = wpautop( get_the_author_meta( 'description', $id ) );

	/** The author box markup, contextual */
	$pattern = $context == 'single' ? '<div class="author-box"><div>%s %s<br />%s</div></div><!-- end .authorbox-->' : '<div class="author-box">%s<h1>%s</h1><div>%s</div></div><!-- end .authorbox-->';

	echo apply_filters( 'genesis_author_box', sprintf( $pattern, $gravatar, $title, $description ), $context, $pattern, $gravatar, $title, $description );
	

}