How to schedule action on parent post

I have a custom amendment plugin enabled on my site, along with post-expirator. How it works is – once a post is published, the user need to first create an amendment of that post, make changes & then publish it. Which then copies the changes to original post.

The issue I’m facing is – after creating amendment, if I enable future action or make chanegs the future action, the scheduler is only scheduled for that amendment since post_id contains id for amendment post, but it doesn’t schedule changes for original post. Earlier it was working fine (till v2.1). Now after upgrading to v3.4, and it used to create scheduler for both amendment & original post. But this has stopped working so I’m not able to schedule changes or update schedules on publsihed posts. I’m already copying post meta from amendment post to original post, how can I make sure that scheduler also is created/updated for original post?