|By William Beechey via Wikimedia Commons|
Augusta was the daughter of a Landgrave of Hessee-Kassel in Germany, and through his mother, was a granddaughter of Britain's King George II. She was, however, more than 20 years younger than her groom when they married in 1818. Following the death of his only legitimate niece, Princess Charlotte of Wales, in 1817, Adolphus had been sent on a mission by his eldest unmarried brother, the third son, William Duke of Clarence. Brothers #1 and #2 were both married to women they despised who were getting too old to have children any way. Brothers #3 through #7 were middle-aged wastrels whose mistresses and illegitimate children were outnumbered only by their debts. With the tragedy of 1817, however, they needed to find suitable fecund brides immediately.
As the next brother in line, William Duke of Clarence was the most urgently in need of a wife. (He would, indeed, eventually become King William IV.) So, he sent the youngest brother Adolphus Duke of Cambridge to check out the princess of Hesse-Kassel for him. Sometimes there can be complications when you send your brother to find you a woman: Adolphus decided he liked Augusta for himself. William conceded defeat and later married Adelaide of Saxe-Meinengen.
The Duke and Duchess of Cambridge spent their first 20 years together in Hanover, where he oversaw the continental kingdom on behalf of his older brothers, George IV and William IV. Following William's death, their niece Victoria (young daughter of brother #4) ascended in Britain but could not do so in Hanover, where only boys were allowed to hold sceptres. So, brother #5 got the Hanoverian throne, and the Cambridges went back to England to finish raising their family, which included son George (future Duke of Cambridge) and daughters Augusta and Mary Adelaide (read her profile.) Through Mary Adelaide, the Cambridges are ancestors of the current Duke of Cambridge: their granddaughter was Queen Mary, who is Prince William's great-great grandmother.
Augusta Duchess of Cambridge has the honor of being George III's longest lived daughter-in-law, living until the age of 91 and missing only the last 12 years of her niece Victoria's long reign. She lived the last 39 years as a widow, but she had nine grandchildren to keep her busy.