According to Charles A. Flagg of the Library of Congress, "The tradition of Thomas is that he loved a girl in station below his own. Their union was opposed by his family, so the two decided to emigrate, and did so, coming in two vessels which sailed in company, and marrying soon after their arrival. We do not know the maiden name of the wife Mary, nor the date of marriage".

The name in England was spelled Fleg and Flegg, a spelling that stil prevails. The lineage of the family has been traced in England to William Flegg, who died in 1426, and various Fleggs and deFleggs are mentioned in English records in the twelfth and thriteenth centuries. The head of the English family was the Lord of the Manor of Flegg Hall, Winterton in the Hundred of East Flegg, count Norfolk.1646

The Flagg, or Flegg family were among the early settlers of New England, Thomas Flegg having left Scratby, hundred of East Flegg, Co. Norfolk, in 1637, and embarked in company with Sir. Richard Carver, from Yarmouth for this country. He settled in Watertown, and was for nine years one of the selectmen of that town. He had eleven children and numerous descendants.1647

Thomas Flagg, settled in Watertown as early as 1643, and was probably the ancestor of all families bearing that name in this country. He was selectman, 1671, 74, 75, 76, and 78. He lost his left eye, by a gunshot accident, previous to 1659, and he died Feb. 6, 1697-8. His will dated Mar. 5, 1696-7.
(Early Settlers of Watertown, Massachusetts, by Henry Bond, M. D. pp.219)