delete rows in parent-child tables found in another parent-child tables

Database

delete rows in parent-child tables found in another parent-child tables

I am loading data into a parent-child pair of tables in a "staging" database schema. If there are duplicate records that were previously loaded into a parent-child pair of tables in a "master" database schema, I want to delete them from the "staging" database tables.

This query

SELECT  A.*,B.* FROM  STG.AUTO_REPR_PAR_STG A JOIN STG.AUTO_REPR_CHLD_STG B ON A.TEST_SEQ_NUM=B.TEST_SEQ_NUM WHERE EXISTS (  SELECT A.*, B.* FROM  MST.AUTO_REPR_PAR A JOIN MST.AUTO_REPR_CHLD B ON A.TEST_SEQ_NUM=B.TEST_SEQ_NUM )

will show what's in staging that was previously loaded in master. But how do I delete from the parent-child pair of tables in staging database? I am drawing a "blank"....I tried this but it bombs ("Tables not allowed in FROM clause"):

   DELETE   FROM STG.AUTO_REPR_PAR_STG A JOIN STG.AUTO_REPR_CHLD_STG B
ON A.TEST_SEQ_NUM=B.TEST_SEQ_NUM WHERE EXISTS (
SELECT A.*, B.* FROM MST.AUTO_REPR_PAR A JOIN MST.AUTO_REPR_CHLD B
ON A.TEST_SEQ_NUM=B.TEST_SEQ_NUM )

Back-end is Teradata v13. I am currently researching the CASCADE DELETE option but I am not even sure it is supported....Any idea?