Genesis related post with category http://www.wptron.com/show-related-posts-genesis-without-any-plugin/

related-post-category.php

/** WPT related post widget */
function wpt_related_posts_cat() {
if ( is_single ( ) ) {
global $post;
$count = 1;
$postIDs = array( $post->ID );
$related = '';
$cats = wp_get_post_categories($post->ID );
$catIDs = array( );{
foreach ( $cats as $cat ) {
$catIDs[] = $cat;
}
$args = array(
'category__in'          => $catIDs,
'post__not_in'          => $postIDs,
'showposts'             => 4,
'ignore_sticky_posts'   => 0,
'orderby'               => 'rand',
'tax_query'             => array(
array(
'taxonomy'  => 'post_format',
'field'     => 'slug',
'terms'     => array(
'post-format-link',
'post-format-status',
'post-format-aside',
'post-format-quote' ),
'operator' => 'NOT IN'
)
)
);
$cat_query = new WP_Query( $args );
if ( $cat_query->have_posts() ) {
while ( $cat_query->have_posts() ) {
$cat_query->the_post();
$related .= '<li><b>'.$count++.'</b>. &nbsp<a href="' . get_permalink() . '" rel="bookmark" title="Permanent Link to' . get_the_title() . '">' . get_the_title() . '</a></li>';
}
}
}
if ( $related ) {
printf( "<div><h3>You'll also like:</h3><ul>%s</ul></div>", $related );
}
wp_reset_query();
}
}
add_action( 'genesis_after_entry_content', 'wpt_related_posts_cat' );