'The Crown' Season 4: What We Know About Queen Elizabeth II's Institutionalized Cousins

Queen Elizabeth II's cousins were institutionalized with severe learning disabilities in a heartbreaking family tragedy brought to life by season four of The Crown.

Katherine and Nerissa Bowes-Lyon were nieces of the Queen Mother and are depicted in the Netflix series as hidden away to protect the shame of the monarchy.

The Queen Mother is even shown claiming the public could not be allowed to discover a possible defection in the royal gene pool in order to protect the perception of a pure bloodline.

The sisters were children of her brother John Herbert Bowes-Lyon, the queen's uncle who died in 1930, and his wife Fenella.

They were admitted to the Royal Earlswood Hospital in Redhill, London, in 1941.

In The Crown, Princess Margaret vists the institution, though she does not go inside.

Helena Bonham-Carter as Princess Margaret, The Crown
Helena Bonham Carter as Princess Margaret in Season Four of 'The Crown' which aired on Netflix on Sunday, November 15, 2020. She is depicted discovering her cousins had falsely been described as dead when in reality they were institutionalized. Des Willie/Netflix

Also mentioned are their cousins Idonea, Etheldreda and Rosemary, children of Fenella's sister Harriet, who had a similar condition.

Their learning difficulties are thought to be hereditary and trace back to Fenella and Harriet's father, Charles Hepburn-Stuart-Forbes-Trefusis, 21st Baron Clinton.

Katherine and Nerissa were wrongly listed as having died in the 1963 and subsequent editions of Burke's Peerage, a reference book to the aristocracy.

Episode Seven even depicts the Queen (played by Olivia Colman) and Margaret getting down a copy of the book to check the listing.

In reality, the secret lives of the two sisters were revealed by The Sun in 1987, the year after Nerissa died, and subsequently confirmed by the Royal Earlswood.

Nerissa's grave was marked only with a plastic marker and serial number, Vanity Fair reported.

A press report from the era carried a Buckingham Palace statement: "We have no comment on it at all. It is a matter for the Bowes-Lyon family."

Katherine Bowes-Lyon died aged 87 in 2014.

February 18th, 1919: Nerissa Bowes Lyon born https://t.co/yJhzgS04zs pic.twitter.com/g7OGzvVV8B

— Jackie (@BritFlorida) February 18, 2016

In The Crown, Princess Margaret (played by Helena Bonham-Carter) is seen berating the Queen Mother over the decision and linking it to her own treatment by the royals.

She says: "Locked up and neglected. They're your nieces—daughters of your favorite brother.

"It's wicked and it's coldhearted and it's cruel. It's entirely in keeping with the ruthlessness I myself have experienced in this family."

In reality, Lady Elizabeth Anson, the queen's cousin, claimed nurses at the hospital asked the family to restrict visitors to avoid upsetting the women, who had a mental age of four.

She released a statement to the Sunday Express after a 2011 documentary was aired on the U.K.'s Channel 4.

It read: "Lady Elizabeth's grandmother, the Honorable Fenella Bowes-Lyon, Her Majesty The Queen Mother's sister-in-law, visited her daughters on a regular basis.

"Indeed, it is clear that she was the only person whom they recognized.

"Others did visit but it seems that both ladies were distressed, if not terrified, by such visitors and the nurses asked the family gently if these could be discontinued."

It added: "Lady Elizabeth can confirm that it was she, together with her late brother Patrick, the 5th Earl of Lichfield, and their cousin Katherine, who organized the headstone for Nerissa Bowes-Lyon.

"For these two very private ladies to have any sort of spotlight turned upon their lives, let alone such a powerful one as provided by national television, appears to Lady Elizabeth to be needlessly cruel.

"She cannot accept that any sort of public interest can be served."