Insert below code at function.php file

add_image_size( 'related', 200, 200, true );

//for XHTML themes
add_action( 'genesis_after_post_content', 'child_related_posts' );
//for HTML5 themes
add_action( 'genesis_after_entry_content', 'child_related_posts' );
/**
* Outputs related posts with thumbnail
*/
function child_related_posts() {

if ( is_single ( ) ) {

global $post;

$count = 0;
$postIDs = array( $post->ID );
$related = '';
$tags = wp_get_post_tags( $post->ID );
$cats = wp_get_post_categories( $post->ID );

if ( $tags ) {

foreach ( $tags as $tag ) {

$tagID[] = $tag->term_id;

}

$args = array(
'tag__in'               => $tagID,
'post__not_in'          => $postIDs,
'showposts'             => 5,
'ignore_sticky_posts'   => 1,
'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'
)
)
);

$tag_query = new WP_Query( $args );

if ( $tag_query->have_posts() ) {

while ( $tag_query->have_posts() ) {

$tag_query->the_post();

$img = genesis_get_image() ? genesis_get_image( array( 'size' => 'related' ) ) : '<img src="' . get_bloginfo( 'stylesheet_directory' ) . '/images/related.png" alt="' . get_the_title() . '" />';

$related .= '<li><a href="' . get_permalink() . '" rel="bookmark" title="Permanent Link to' . get_the_title() . '">' . $img . get_the_title() . '</a></li>';

$postIDs[] = $post->ID;

$count++;
}
}
}

if ( $count <= 4 ) {

$catIDs = array( );

foreach ( $cats as $cat ) {

if ( 3 == $cat )
continue;
$catIDs[] = $cat;

}

$showposts = 5 - $count;

$args = array(
'category__in'          => $catIDs,
'post__not_in'          => $postIDs,
'showposts'             => $showposts,
'ignore_sticky_posts'   => 1,
'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();

$img = genesis_get_image() ? genesis_get_image( array( 'size' => 'related' ) ) : '<img src="' . get_bloginfo( 'stylesheet_directory' ) . '/images/related.png" alt="' . get_the_title() . '" />';

$related .= '<li><a href="' . get_permalink() . '" rel="bookmark" title="Permanent Link to' . get_the_title() . '">' . $img . get_the_title() . '</a></li>';
}
}
}

if ( $related ) {

printf( '<div class="related-posts"><h3 class="related-title">Related Posts</h3><ul class="related-list">%s</ul></div>', $related );

}

wp_reset_query();

}
}

Insert below css code at style.css

/*-------------- Related Posts --------------*/
.related-posts h3 {
color:#101010;
font-size:18px;
}
.related-posts {
overflow: hidden;
}
.related-list li {
float: left;
list-style-type: none;
margin: 0 20px 0 0;
text-align: center;
width: 140px;
}
.related-list img {
background:#f0f0f0;
border: 0px;
display: block;
margin: 0 auto;
padding: 0px;
}