Among many other controversial storylines, the British royal family has been left most "frustrated" about the seventh episode in the recently-released season 4 of "The Crown." The episode titled "The Hereditary Principle" shows Queen Elizabeth II's secret cousins who according to the series were registered deceased in papers but hidden away in a mental institution in reality.

In the heartbreaking episode, the queen's sister Princess Margaret who is struggling with mental health issues, discovers that her two cousins were essentially abandoned by the royal family so that their mental illness could not affect the royal family's reputation. The cousins named Katherine and Nerissa Bowes-Lyon, along with a few other relatives, lived at an institution in Surrey until they passed away.

While many of the scenes in the Netflix series have been fictionalised, the end credits of the episode show that the story about the cousins is based on facts. In the fictionalised version, when the late Princess Margaret asked the Queen Mother about the decision to hide her own nieces and portray them dead, she was told that it was done in order to avoid questions about the sanity of the bloodline in power.

Nonetheless, the British royal family is reportedly miffed with the show's depiction of Katherine and Nerissa being abandoned by them. David Bowes-Lyon, whose father was the late Queen Mother's first cousin once removed, told The Telegraph that the royals are "frustrated" with their negative portrayal.

Noting that he is probably the only member of the family who could publicly say anything about the controversy, David said: "I wouldn't say there is upset in the family, but I think people are frustrated and would like the record put straight."

Even though the episode suggests that Princess Margaret presumed her cousins dead, David says she was aware of exactly who they were and where they were kept.

"She knew who they were in every respect, as you would any cousin. She knew exactly who they were and what had happened. It is completely wrong to say they were forgotten and certified as lunatics," he said.

He also said that the sisters were not "abandoned" but "frequently" visited by the members of the family. However, a report in Daily Mail in 2011 notes that the last known royal visit to Katherine and Nerissa was in the 1960s.

British Royal Family
Senior members of the British Royal Family Photo: AFP / Tolga AKMEN