Joins With 3 Tables

Hi my problem is quite easily determined for most of you.

In the GridView, I see my main table and have it connected to the subsidiary table. Now I would like to include more infomation the 3rd table. The FK the 3rd table is the daughter table.

So far I’ve followed this guide: is-related-fields-in-gridview-yii-2-0/

How do I embed a another table on the 2nd?

User renderpartial to load view of another model into desired one.

 echo $this->renderPartial('//agreement/admin',array(

        'model'         => $agreement_model,