I found the Boone Family Tree which contains your relatives. I've asked the owner to contact you because this tree is extensive.
An Emil Robert Feuz b. 24 May 1880 was living in Shasta Co., CA in 1917 or 1918. Source: World War I Draft Registration Cards 1917-1918.
An Emil Robert Feuz b. Switzerland was naturalized 25 Feb 1920 in Superior Court. Source: Shasta County, California Naturalization Records 1852-1932.
A Juliet H. Feuz b. 11 Jan 1913, Shasta Co. Mother's Maiden Name=Williams. Source: California Birth Index 1905-95.
A Juliet H. Feuz b. 11 Jan 1913, CA died 9 Oct 1941, Mendocino Co. Mother's Maiden Name-=Williams. Father's Surname-Feuz. Source: California Death Index 1940-97.
You can request a copy of her obituary from the Held-Poage Research Library @ pacificsites.com/~mchs/ .
You can also contact Random Acts Genealogical Kindness. Go to raogk.org, read guidelines, choose California, choose Mendocino Co. and choose one volunteer.
An Ella L. Feuz was born 9 June 1914, Shasta Co. Mother's Maiden Name=Williams. Source: California Birth Index 1905-95.
I didn't find anything else for her and she might have died early. You can request a volunteer at RAOGK to check into this.
An Elizabet L. Feuz was born 21 May 1919, Shasta Co. Mother's Maiden Name=Williams. Source: California Birth Index 1905-96.
According to the Boone Family Tree she married Hubert Boone in 1948.
An Elisabeth Lidia Boone b. 22 May 1919, CA died 14 Nov 1979, Santa Clara Co. Source: California Death Index 1940-97.
Check the Santa Clara County Library or RAOGK for her obituary.
Hubert Boone emigrated from Edmonton, Canada with his family 24 Dec. 1919 to Eastport, Idaho, USA.
S____ Boone, head household, 38, married, farmer.
____ Boone, wife, 34.
McDonald Boone, son, 6.
Hubert Boone, b. abt. 1915.
Samuel Dolar, son, 2.
Mr. Boone's mother was living at Battle Ridge, Alberta, Canada.
Race or People: Unknown
Source: Seattle Passenger and Crew Lists 1882-1957.
A Hubert B. Boone b. 25 Aug 1915, Last Residence=Palo Alto, Santa Clara Co., CA died 1 July 2008. His soc. sec. # was assigned in CA before 1951. Source: Soc. Sec. Death Index.
An Emma A. Feuz b. 26 June 1917, Shasta Co. Mother's Maiden Name=Williams. Source: California Birth Index 1905-95.
An Emma Fuez b. 26 June 1917, Last Residence=Palo Alto, Santa Clara Co died 1 Feb 2005. Her soc. sec. # was assigned in California before 1951. Source: Social Security Death Index.
According to the Boone Family Tree, Henry Edward Williams b. Oct. 1856, Connecticut. He married Anna Maria Rasmussen 14 June 1893, Shasta Co.
In 1900 Henry, Anna and Juliette were living in Burney Valley, Shasta Co.
In 1910 all three were living in Burney Valley.
In 1920 Henry & Anna were living in Burney.
In 1930 Henry & Anna were living in Township 7, Shasta Co.
I'd say Henry and Anna didn't have any other children than Juliet.
I don't know if Henry came alone or not to CA because the earliest Census I could find was the 1900. Successful Searching!