def is_sibling_of(page1, page2):
    """
    Determines whether a given page is a sibling of another page

    ::

        {% if page|is_sibling_of:feincms_page %} ... {% endif %}
    """

    try:
        return _is_sibling_of(page1, page2)
    except AttributeError:
        return False

    Determines whether a given page is a sibling of another page

    ::

        {% if page|is_sibling_of:feincms_page %} ... {% endif %}
    
feincms/templatetags/feincms_page_tags.py