http://hartgen.renderplus.com/htm/littlefield.htm

At about the age of 7 or 8 he disappeared from his father's house. That he was born about 1619 is supported by the fact that he was required to sign the submission to Massachusetts in 1653. This Francis did not come over with his mother on the Bevis.
(Source: History of Wells and Kennebunk pg 73-74)

(From Noyes, Libby & Davis; Genealogical Dictionary of Maine and New Hampshire; p.438): The oft-told story of his separation from his family was the imagining of some one trying to account for two brothers of the same name, and not unlikely he accompanied his father here, but moved around before settling in Wells, where (he was) granted 50 acres by Orges in 1643.

There is no basis for the local lore that Francis was somehow separated from his family.

That much-romanticized story evolved from a historian's attempt to explain Edmund having two
sons with the same name.

Charles Thornton Libby [2.1 suggested that this situation came about as a result of the custom

of letting the godfather select the infant's name.

Using the LDS IGI files [see Austin] we learn that Annis Austin had a brother Francis Austin who died young.

The most likely scenario is that Francis Jr. who was bp. in Titchfield 24 March 1635/6,

(after his father "absented himself") was named in memory of his maternal uncle,

whereas Francis Sr. had been named for the paternal side of the family.

C. T. Libby's suggestion applies well to this theory.