Sadly your parents REGISTERED the children. You can't UN-Register them.
HOW would you apply it? CUSTODY is a legal term. If you DON'T want custody, notice of mistake is good for that. ALL "Legal responsibility" for the child would be removed...
...I can't think of any other way to apply it.
Printed copy · Anthology Volume 1, page 158Printed copy from The Tender For Law Anthology, Volume 1, page 158 (printed 14 June 2014). Added by this site; not part of the Facebook export.