@JWiberg sadly, there is no "relation" between a child and a parent page. The only relation there is, is if it's in the same URL Path or not.
You can do multiple things to "trick" a parent:
1. Base the Parent on the URL path
Based on that URL path, you can grab the URL and a fake title that might not be the same as the parent, but is fairly ok.
As an example, here are breadcrumbs we made based of the URL.
The home is the default website URL and name. Projecten. the parent, is based of the URL (example.com/projecten/nieuwe-bestrating-maakt-wijkcentrum-druten-helemaal-af).
Let me know if you need the code for this 🙂
2: Create a module where you need to select the menu
This way, you can show the parent in the menu, where you want to. Create a module, load the selected page and you are done!
Yet, you need to set this on every page. Lot's of manual work.
3: Create a custom menu that you load on every page and contains every page on your site.
Hide all items of the menu but the second to last. I think that should do the trick, but gets buggy real fast.