Birth and early life
The circumstances surrounding Harriet's illegitimate birth involved much secrecy. By the end of 1799, Henrietta Ponsonby, Countess of Bessborough had discovered she was pregnant by her longtime lover, Granville Leveson-Gower. The consequences of such an event could be potentially disastrous; eight years earlier, Lady Bessborough had witnessed the scandal and emotional turmoil experienced by her sister Georgiana, Duchess of Devonshire, when her own illegitimate child had been born. Lady Bessborough was also terrified that her husband would discover the truth and divorce her. Undoubtedly aided by the era's empire waist fashions, she succeeded in hiding the pregnancy from him – only a few close family members and friends were made aware.
The child, Harriette Arundel Stewart, was born in mid-1800; her given surname was inspired from Leveson-Gower's mother Susanna Stewart. To her lasting sorrow, social constraints prevented her from openly acknowledging the child. Illegitimate children were increasingly disapproved of in English society; worrying about her daughter's future, Lady Bessborough arranged for her to be raised by a foster mother. Another illegitimate sibling, George Arundel Stewart, was born two years later in similar circumstances.
Both parents remained in close contact with their children and monitored their progress. Though they lived apart, the Countess sought to be involved in her daughter's life, serving as a sort of godmother to the child. Lady Bessborough wrote frequently to her, though most of these letters were later destroyed. One of the few surviving letters reveals that when the girl was two years old, her mother purchased a locket and asked Leveson-Gower for a piece of his hair in which to send to their daughter.
Harriet's life changed quite significantly in August 1812, when she was brought to live in her father's household at Tixall Hall in Staffordshire. At first this was meant to be a temporary visit, but Leveson-Gower's new wife Harriet took to the girl and wished her to stay, describing her as "a most amiable little creature and though she has nothing precose about her, her intelligence and docility make her a very delightful companion." "Little Harriet", as she was known, was loved and included as one of the family, which contained five younger half-siblings as well as her brother George Arundel Stewart. She was never informed of her true parentage, and referred to Leveson-Gower as "her guardian."