How to link a form inputs to each other

I have a form that has multiple inputs. Like parent and child.

1. Activity 1
   1.1 Sub-activity 1
   1.2 Sub-activity 2
   1.3 Sub-activity 3
   

2. Activity 2
   2.1 Sub-activity 1
   2.2 Sub-activity 2
   2.3 Sub-activity 3
   

These parents and child are generated dynamically. By this I mean that I can create multiple of them by clicking on add more button with jQuery .

My question is that how should I save them that when I want to fetch it back from database then every child should be under its parent.

I am using laravel 5.

via Chebli Mohamed