John’s exact relationship to his contemporaries, Henry and Richard Cock*, is unknown, but it seems most likely that he was Henry’s brother and Richard’s uncle. It is possible that Robert Cock, mayor of Sandwich in 1470-1, was his son, while another kinsman, William, served as jurat in the 1470s and fathered John†, who sat in the Parliament of 1510 .
John was already one of the jurats when he was elected to his first Parliament, alongside Robert Wilde*, on 9 June 1433.
It is unclear how Cock made his living, although he and other members of his family were holders of land outside Sandwich. In 1430, 1435 and 1442 John claimed exemption from the parliamentary subsidy in Wingham hundred, and by the last date he had also added interests in Eastry hundred.
