Conversation so far:
Where was Walter O'Malley born?
Walter O'Malley was born in the Bronx, New York
Who was Walter O'Malley father?
Walter O'Malley's father was Edwin Joseph O'Malley
What did Walter O'Malley father do?
Walter O'Malley's father was a cotton goods salesman

Question: Who was his mother?
Self-contained rewrite: Who was Walter O'Malley mother?