Interesting. Who was “mother”?
Sometimes a cigar is just a cigar...Oedipus complex?
Good question. Probably another reference to Tran Le Xuan, aka Madame Nhu, the de-facto "First Lady" of South Vietnam, although she was safely out of the country on a tour to try to rally support for the Diem government. "Brother" would have been Ngo Dinh Nhu, her husband and President Diem's brother, who was also killed in the coup.
Some other references--"summer rain" (the wet monsoon that brings rain to Vietnam during the summer), "some stranger's hand" (foreign economic and military aid), "insane children" (South Vietnam's coup-happy military elite), "Roman wilderness of pain" (government-by-coup, similar to ancient Rome), "the King's Highway" (Route 1, leading toward the old royal capital of Hue), "The West" (SEATO and NATO), "seven miles" (the seven members of the Warsaw Pact).