From Joan S. Guilford, "The Ancestry of Dr. J. P. Guilford, Vol. 1," (1990),
p. 322-323:
"Supporting the notion that the [Guilford] family came from Kent, England, is the marriage of John1 Guilford to Susanna Knowlton, daughter of William1 Knowlton, since the latter is known to be from Kent and since he was a seafarer and owned his own ship. It is believed that these families traveled together and it is assumed that after Mary (----) Guilford and her son John1 died, Ann (Smith) Knowlton took in the
children of John1 and raised them. There has been a great deal of dispute as to whether Susanna was a Knowlton or a Norton, there also being a William Norton in Hingham at the time, but this writer believes the evidence in favor of Knowlton is overwhelming.
For a discussion of this controversy, see the Knowlton family [in the same book, pp. 516-21]."