templates/inc/related-topics.html

<div class="related-topics">
    <h3 class="related-topics-header">Related</h3>

    {% for related in page.related %}
        <ul class="related-topics-list">
            {% for post in site.posts %}
                {% if related.title == post.title %}
                    <li class="list-item">
                        <a href="{{ post.url }}">{{ post.title }}</a>
                    </li>
                {% endif %}
            {% endfor %}
        </ul>
    {% endfor %}
</div>