Her paternal grandfather was the son of the 3rd Baron Stafford and Lady Mary Stanley (a daughter of the 3rd Earl of Derby).
"[2] Following her brother's death in 1637, and the forced (and probably illegal) surrender of the barony, on the ground of his poverty, by the next heir, Mary's distant cousin Roger Stafford in 1637, the Howard family secured the title for William.
Mary and William were both attainted on 7 December 1680 as Royalist supporters, before being falsely implicated by Titus Oates in the later discredited "Popish Plot".
[a] Mary had her titles restored with the accession of James II, and was created 1st Countess of Stafford, for life, on 5 October 1688 in the Peerage of England, as a consolation for the failure to reverse the attainder on her husband.
At the same time, her eldest son, Henry, was created 1st Earl of Stafford, with a special remainder to his brothers and their male issue.