In an instance such as this, you can just delete the application from onBoard > People Finder > Checklist tab and have the parent fill it out again.
Tip: To make the process seamless for the parent, print the PDF for the application in the candidate's record. Then impersonate the parent, click on their child's name on the left and start the application for them filling in the information they already provided on the original application form. This way the parents can continue where they left off instead of starting from scratch.