I am getting duplicate nodes on my family tree - php

Question

My function is duplicating some nodes on the tree. When I am calling that function in a recursive way. I have a database table of all father, mother, wife, husband, child ids. I am taking all persons from their father id only. I don't know from where these extra nodes are coming and how should I handle ie it. Output image
<?php
function categoryTree($parent_id = 0,&$alreadyThereArr=array())
{
$ci =& get_instance();
//$query = $ci->db->query("SELECT * FROM tbl_user WHERE father_id = $parent_id ORDER BY id ASC");
$sql="SELECT * FROM `tbl_user` WHERE father_id = '$parent_id' ORDER BY id ASC";
$query=$ci->db->query($sql);
$result=$query->result();
if(count($result) > 0)
{
echo '<ul>';
foreach($result as $key)
{
if(!in_array($key->id,$alreadyThereArr))
{
//echo 'In';
if($key->wife_id != 0)
{
//echo 'wife';
$wife=$ci->Main_M->getSingleRow('tbl_user','id',$key->wife_id);
$start='<div>
<span class="male">'.$key->name.'</span>
<span class="spacer"></span>
<span class="female">'.$wife->name.'</span>
</div>';
}
else
{
$gender=($key->gender == 'M') ? 'male' : 'female';
$start='<div><span class="'.$gender.'">'.$key->name.'</span></div>';
}
$alreadyThereArr[]=&$key->id;
echo '<li>';
echo $start;
echo '<ul>';
categoryTree($key->id, $alreadyThereArr);
echo '</ul>';
echo '</li>';
}
}
echo '</ul>';
}
//print_r($alreadyThereArr);
}
?>