They were indeed, although, there was some controversy regarding the supposed filming dates of this movie. All they'll say is that it was filmed before July's end in 1969, they were born on July 22nd 52'. Sadly, Madeleine died in August last year(2014) she was 62. A tragedy.
I've been a fan of Mary & Madelline ever since I discovered their Playboy layout,long after it was published. I've hunted for their films but never found any except Twins of Evil. Many thanks for posting this one.