Admiralty law
He was born around 1570, sixth son of John Ryves of Damory Court, near Blandford, Dorset, and Elizabeth Mervyn. He belonged to a gifted family: one of his brothers, Sir Thomas Ryves, was considered to be the leading expert on ecclesiastical and Admiralty law of his time, and another brother George was Master of New College, Oxford. Dr. Bruno Ryves, royal chaplain and later Dean of Windsor, was his first cousin, and Sir John Davies, whom William replaced as Irish Attorney General, was his uncle by marriage.