How might I find a render array of a parent OG group?
I did the following to achieve this. I'm still not happy with the results but given time pressures, it'll have to do. I'm posting to see if anyone can suggests a better alternative. 

I grab the nid of the parent group first and use it to do a query against menu_links. Once I have a result of a menu_id(s), we loop through, get the links, use theme(), and then drupal_add_region_content(). 

&lt;?php
/**
 *
 *
 * This module creates a block that looks for any parent OG group and displays the menu of that
 * group. 
 */

define('_OGPN_NODETYPE', 'user_posted_content');
define('_OGPARENTNAME_TITLE', 'OG Parent Menu');


/**
 * Implements hook_block_info().
 */
function ogparentmenu_block_info() {
    // This example comes from node.module.
    $blocks['_ogparentmenu'] = array(
        'info' =&gt; t(_OGPARENTNAME_TITLE),
        'cache' =&gt; DRUPAL_NO_CACHE,
    );


    return $blocks;
}

/**
 * Implements hook_block_view().
 */
function ogparentmenu_block_view($delta = '') {
        return [
            'subject' =&gt; t(_OGPARENTNAME_TITLE),
            'content' =&gt; __ogparentmenu(),
        ] ;
}


/**
 * @return string
 * @throws Exception
 */
function __ogparentmenu() {

    $node = menu_get_object();

    /* Set up menu on UserPosts  */
    if ($node-&gt;type == _OGPN_NODETYPE) {

        // get parent link of og
        $parent_og = filter_var($node-&gt;og_group_ref[LANGUAGE_NONE][0]['target_id'], FILTER_SANITIZE_NUMBER_INT);

        // Query menu_links based on node/$nid path
        $menu_query = db_select('menu_links', 'ml')
            -&gt;fields('ml', ['menu_name', 'mlid'])
            -&gt;condition('link_path', "node/$parent_og", '=')
            -&gt;execute();

        // if single
        if ($menu_query-&gt;rowCount() == 1) {
            $menu_id = check_plain($menu_query-&gt;fetchAs()['menu_name']);
            $links = menu_navigation_links($menu_id);

            $themed_menu = theme('links__system_main_menu', [
                '#title' =&gt; t('title'),
                'links' =&gt; $links,
                'attributes' =&gt; [
                    'class' =&gt; ['user_post_menu_injected', 'section']
                ],

            ]);

            return $themed_menu;





        }
        // TO DO : handle multiple
        elseif ($menu_query-&gt;rowCount() &gt; 1) {

            return 'null';
        }



    }
}