I have it set up where a single "cluster" record displays information from the parent records.
Hmm "parent-child" usually describes a single parent record matching to many child records--which is not the case here so your terms can be a bit confusing.
I would like my users to be able to remove an individual parent-child record on the join table. I am not certain how I can do this with records displayed via a portal, however.
You can put a button in the portal row that deletes that portal row record if you allow deletion in Portal setup. I even have a script for that which is a bit more user friendly in the confirmation message that's displayed. You can import a copy from the Known Bugs List if you want to try it out. It is designed to import error free into an FileMaker file and the one script can work with any portal in your file.