How can I get the saved value in the variable table to show on a form?
You'll have to refer to the Form API docs for radios for tips.

Second, it might make things easier to reason about if you do:

$one = variable_get('one', array('visibility' =&gt; 0));
$is_visible = $one['visibility'];

$form['one']['visibility'] = array(
 '#type' =&gt; 'radios',
 '#title' =&gt; t('The title'),
 '#options' =&gt; array(0 =&gt; t('Yes'), 1 =&gt; t('No')),
 '#default_value' =&gt; $is_visible,
);