At the death of her brother
Humphrey, 2nd Earl of Buckingham, in 1399, Anne was the co-heiress together with her two sisters Joan and Isabel, to his estates and titles. Anne became the sole heiress of the family's estate and titles in 1400, as one of her sisters, Joan, having died on 16 August 1400, and the other, Isabel, having become a
nun. She was subsequently recognized (and thereafter succeeded) as
suo jure Countess of Buckingham, Hereford and Northampton as well as succeeding to the titles of Lady of Brecknock and Holderness. Anne did not, however, use these titles, and instead styled herself as Countess of Stafford. On Anne's death, in 1438, the title of Buckingham (as well as her other titles) passed to her son
Humphrey Stafford, Earl of Stafford, who in 1444 was created Duke of Buckingham. This title remained in the Stafford family until the
attainder and
execution of
Edward Stafford, 3rd Duke of Buckingham, in 1521. ==Marriage with Thomas Stafford, 3rd Earl of Stafford==