If you want details of the Shirley family then Stemmata Shirleiana; or the Annals of the Shirley Family. Lords of Nether Etindon in the County of Warwick, and of Shirley in the County of Derby. 2ed. London: Nichols and Sons, 1873 is the book you need to consult.
Despite my old Mother insisting that "we are connected to Lord Ferrers" I think it was just a family tradition. Though the Sewall name does appear as a Shirley first name I have found no connection (blood-wise) between Henry Sewall and the Shirleys or the Ferrers.
I guess the line you are thinking of reads:
Sasuualo, Lord of Etendone (Eatington). fl. 1079-1086
Fulcher, held lands in Shirley d. by 1165
Sewallis de Syrle. Lord of Eatington, living 1192 m2 Matilda Ridel
Henry, Lord of Eatington fl 1205-6
Sir Sewallis de Eatington, knt. fl 1251-2 m Isabel Meysnyll (widow of John de Neville)
Sir James de Shirley, knt. Lord of Eatington fl. 1278 m Agnes de Walton
Sir Ralph Shirley. knt ob. 1327
etc.
John