What it did remind me of was Gloria's mother who would, I guess, be Big Gloria. In the documentary, Gloria said she was made to have daughters and she would have named her first daughter, Gloria. Alas, she had four sons.
The first Gloria Vanderbilt began life as a Morgan and as a twin. Gloria and Thelma Morgan were known collectively as "The Magnificent Morgans." They were the offspring of Harry Hays Morgan, an American diplomat and his Chilean-born wife, Louise Valdivieso. It was Louise, testifying while clutching her crucifix, who may have been the final nail in Big Gloria custody coffin, when she testified to the wild and largely invented nature of Big Gloria's lifestyle.
In 1958, The Magnificent Morgans collaborated on a memoir, Double Exposure. The sisters spilled the beans on the good , the bad, and the ugly, not to mention the the loved, the lost, and the licentious.
The Kirkus Review wrote:
Written with good taste, but sparing no detail no matter how unorthodox, this autobiography of two women is a biography of an age, an age of fantastic extravagance and rigid form, an age in which the various episodes unfolded here seem probable for all their bizarre and melodramatic overtones. Superbly entertaining.Nearly 60 years later, it remains superbly entertaining.
While this book is one of those highly collectible tomes, growing increasingly expensive in a nice dust jacket, you can give it a read on the Internet Archive here.