How to get linked orders in Laravel

I am actually working on a multivendor order system. Here is my order table.

+----+--------+--------------+------------+-----------------+
| id | userid | bookstore_id | payment_at | parent_order_id |
+----+--------+--------------+------------+-----------------+
|  1 |      1 |            2 |   null     | null            |
|  2 |      1 |            3 |   null     | 1               |
|  3 |      1 |            1 |   null     | 1               |
+----+--------+--------------+------------+-----------------+

Now, whenever a user places an order with the same bookstore, the quantity is updated, and when a user creates an order with a different bookstore, the new order is created. Now what I want here is to link child orders with parents’ orders, so for that I have added parent_order_id column where I can put the order id of the parent order. Basically, when I view the details of order id 1, then I want to show the order with id 2,3 in linked order, and when I view order 2, then order 1,2 like that.