How to check if page is child of some exact page?

Hello. Imagine that pages with id 3, 4, 5 are childs of page with id 1

How to check if for example page id=3 is child of id=1?

I am creating some plugin which on load of page should check if page is child of page id=1 and if yes, do something.

I know that i can use $wpdb and check it directly in database but maybe wordpress has some conditional tag or some function for this?