Creating a parent/child with the rt CLI

I’ve looked through the rt CLI help and the wiki but I don’t seem to see
any information about how to create parent/child ticket relationships or
edit pre-existing tickets’ parent/child relationships.

I’m looking for something like.

./rt edit ticket/89999 set MemberOf=87472
./rt edit ticket/89999 set Parents=87472

This seems to work for other fields like status

./rt edit ticket/89999 set status=‘open’

But setting trying to set the parents field (or any of the other
associative fields) gives the error …

memberof: Unknown field.

Thanks for the help