sheila had suffered mental health problems before the twins were even born, when she was on a modelling assignment in hong kong she wrote a letter to colin asking him to book her an appointment with a psychiatrist for when she arrived back in england.
the day june caught them sunbbathing in the fields surrounding WHF sheila had recently had a termination, but she still had her pregnancy shape and liked it, so colin took photos of her with sheilas consent of course.
when june caught them she was furious and called sheila the devils child, colin said himself that from that day sheilas mental condition became worse.