You need to set a meta query to filter the posts by the relationship field on the events. See 3. Multiple custom field values (array based values)
Note that since the field stores ID values you also need to have your values in quotes. The value you are looking for is the current post ID.
$args['meta_query'] = array(
array(
'key' => 'field_name', // name of relationship field on events that relates this post to the events
'value' => '"'.$post_id.'"',
'compare' => 'LIKE'
)
)
