This will probably be my last post here as I am hitting walls and lack the resources to persue this further without speculating and making more mistakes. Hopefully these clues will help someone and not confuse them.
Because Samuel is living with William D.S. Fernald in 1850. I am assuming that he is his brother.
Internet sources link William D.S. as the son of William S. Fernald and Elizabeth Hayden married 14 Sep 1817 in Quincy, Norfolk, MA. Other children listed for William and Elizabeth are: William b. 24 Jul 1819, d. 27 Sep 1820 in Quincy, MA. and Caroline Miller Furnald b. 2 Aug 1818 in Quincy, MA.
Also in 1850 Randolph, MA, one more Fernald is listed. Mary E. Fernald age 20 in the Wale household. I am assuming/suspecting she is most likely the sister of Samuel and William. As her age matches the census and they are the only Fernald's in Randolph.
From the 1840 census because the location, ages and number of children match previous census. I am assuming Elizabeth Fernald of Ward 12 in Boston is the wife of William S.
Here are a couple of brick walls. William S. Fernald may be William Stacy Fernald of Kittery, ME. But Internet sources say he married Elizabeth Batson. One pedigree file on the LDS source has Elizabeth Batson or Hayden. But then he is reported to have died in Kittery 1854. I can not find him nor Elizabeth indexed in the census for Maine nor MA in 1850. (from my earlier post, the Mrs. Fernald I saw in Boston 1850 has too many children.)
On a wild guess, I am thinking perhaps he died before 1840 in Boston and Elizabeth remarried. Then perhaps she died by 1854. The will may have been depositioned in Kittery, where William was from and may still have had property.
from the census:
1820 Quincy, Norfolk , MA William S. Fernald1xx1x1xx1x 1 male 0-10 (perhaps 1st son William who d. in Sept 1820) 1 male 26-45 (head perhaps William Stacy Fernald b. 1790) 1 female 0-10 (dau. Caroline b. 1818) 1 female 26-45(wife Elizabeth)
1830 Boston Ward 12, Suffolk, MA William S. Fernald11xxxx11x1xx1 1 male 0-5 (son William D.S. b. 1827) 1 male 5-10 (unknown son b. 1820-1825) 1 male 40-50(head William S.) 1 female 0-5(dau. perhaps Mary E. b. 1830) 1 female 10-15 (Caroline b. 1818) 1 female 30-40(wife Elizabeth)
1840 Boston Ward 12, Suffolk, MA Elizabeth Fernaldx111x1xxxx1 1 male 5-10(son Samuel b. 1833) 1 male 10-15 (son William D.S. b. 1827) 1 male 15-20 (unknown son b. 1820-1825) 1 female 5-10 (dau. perhaps Mary E. b. 1830) 1 female 40-50(widow? Elizabeth)
Remember, that these are clues and they would need to be researched and verified further before taking my assumptions as fact.
One curious possibility for the unknown son I have listed for William and Elizabeth Fernald is: George H. Fernald b. abt 1822. He is in the 1850 Census for Boston, Ward 12 age 28 with wife Sarah age 30 and dau Frances age 3. He was a moulder.
The LDS familysearch web site has a George Haden Fernald married to a Sarah C. Curtin on 02 APR 1846 in Lynn, Essex, MA. Although Lynn is just north of Boston, It's interesting that his middle name "Haden" sounds pretty close to Elizabeth's proported maiden name of "Hayden". And I can find no other couples named George and Sarah Fernald in MA in 1850.
In 1860 Boston, Ward 12, George and Sarah are 39 and Francis is 13.
In 1870 Boston, Ward 12, George is age 48, wife Sarah E. age 50, dau. Frances A age 23 and there is a Samuel H.W. age 23. ( I don't believe he is a Fernald, I suspect he is the husband of Frances, Samuel H. Wise.)
In 1880 Boston, Sarah E. is age 60 she is the mother in law of Samuel H. Wise age 24 (should be 34) with children Samuel F. age 5 and Arthur age 3.
In 1900 Samuel Wise age 55 was b. in May 1845, confirming the wrong age given in 1880, his sons still live with him.
But again I must state these are just clues, It may be just a coincidence that George H. is the correct age, living in the same ward of Boston as Elizabeth was from, and a George Haden Fernald who also married a Sarah has a middle name that just happens to sound like Hayden!
It looks like there are still a number of disconnected Fernalds out there!!