Born on 11 January 1812, she was the eighth child of George Howard, 6th Earl of Carlisle, and his wife Georgiana, sister of the 6th Duke of Devonshire.

[1][2] The latter, known as the "Bachelor Duke", favoured Blanche and it has been suggested that his decision not to marry and have children of his own may have been coloured by his affection for her and her husband.

"[3] Blanche's unmarried maternal uncle, the Duke of Devonshire, favoured a marriage between his heir, William Cavendish, and his niece.

Before the couple were even introduced, the Duke made preparations; he held a ball for Blanche, then seventeen years old and, weeks later, William proposed to her and was quickly accepted.

The 6th Duke completed his reconstruction of the house in the year of her death, 1840, and constructed an "Urn to Blanche" at the top of the Long Walk in the gardens.