This 1998 song by the Manic Street Preachers was inspired by sisters June and Jennifer Gibson, known as "The Silent Twins" because they only communicated to each other.
The sisters were Yemeni-born twins who were raised in Wales. As children, more significantly as the only Black children in their school, they were often bullies. They spoke a particular form of Creole which made them hard to understand. Soon their language became more incomprehensible, making it impossible for others to understand and became an example of cryptophasia with each girl mirroring the other. In the end they spoke only to each other and to their younger sister, Rose.
Both girls turned to writing fiction, writing novels that were self-published. They were unable to find any professional markets for their work. They then turned to various sorts of crime, including arson. They were committed to the high security Broadmoor Hospital. As juveniles, they were supposed to be there only two years but remained incarcerated for 14 years, heavily medicated on antipsychotic drugs.
The sisters had an agreement that should on of them die the other would begin speaking. Later, they felt it was necessary that one of them die and Jennifer said it should be her. In 1993, they were transferred to more open clinic. When they got there, Jennifer could not be wakened and soon died of a myocarditis. No drugs or poisons were found in her systen and it appears she may have just willed herself to death.
In honor of the twins' birth 56 years ago, here's the Manic Street Preachers.