You may have all of the below, but I needed the background for the research:
The 1900 US Census for Friend School, Township 21, Cherokee Nation, Indian Territory (Eastern half of Oklahoma)
William Rhines, head, Oct 1840 in Tenn.
Elizabeth, wife, May 1852 in IL
Jas H., August 1872 in IL
Imia/Imis?, Aug 1874 in IL
Oscar, Nov? 1874
Border Crossings from Canada to the US.
James Henry Rhines, age 42, born in Odin(?), Ill, farmer, Irish ancestry, 5'-8".
Mary Ethel Rhines, age 27, born in USA, "Trinidad?"
Dora Helen Westhaver(?), age 24, with Friend James H. Rhines, born Halifax, Canada.
--all three enroute to Ontario, California. The Rhines had no relatives in the place of origin; Dora had a Mrs Edward C. Westhaver in Macleod, Alberta
-James had previously been in the US from birth to 1902(difficult to read) in Missouri, Kansas, and Illinois
The 1930 Census for Pleasant Prairie, Spokane County, WA
James H. Rhines, 57, born in IL to father born in IL, mother in TN (backward of what was given in 1900), farmer/truck farmer
Ethel, age 42, born in Colorado.
Grace, May 1883, MO
Samuel, Nov 1887, KS
Harry, Oct 1890, OK
James Henry Rhines initiated the naturalization process with his Declaration of Intention, signed 16 November 1935. He and his wife Mary Ethel Rhines were living in Pleasant Prairie, Hillyard, Spokane Co, WA. He was born in Marion County, IL on August 11, 1872. He was married on December 22, 1909, at Macleod, Alberta, Canada. Mary was born in Trinadad, Colorado on December 10, 1888. There is an image of the document available if you do not have it.
Going back to Canada:
The 1911 Census of Canada
James H. Rhines, born August 1828(obviously a mistake), age 33 (would have been 1878)
Mary E. Rhines, Wife, born Dec 1888, 23.
--The 1906 Canadian Census did not include Macleod in transcription.
--The 1901 Canadian Census was checked, but from above he did not enter Canada until 1902.
The Social Security Death Index:
Ethel Rhines, born 10 Dec 1888, died Sept 1971 in Jerome, Jerome Co, ID. Her SSN: 431-24-5029, was issued in Arkansas before 1951. You can obtain a copy of the image of her application for this card from the Social Security Administration. It would identify where she was living, and spouse. She "might" have obtained one due to going to work, or for financial protection in the future.
You didn't identify which brother, or place of death. If the brother died in 1951, where? If Mary Ethel's SSN was issued in Arkansas before 1951, could they have been living with/near the brother up to that time-frame? SSN's were first issued in 1936; but, they were not issued to farmers or those self employed, military, government employees.
I'd suggest obtaining Ethel's obituary (if one was published in Jerome).
Jerome County has a limited website: http://www.rootsweb.ancestry.com/~idjerome/
There is one volunteer (But only does high school annuals), but you might contact to see if he would search for an obit. It doesn't appear her name is listed in the Jerome City Cemetery; but she could have been moved to the location where he was buried. Today, Jerome has about 8,000 in population.
I looked through these without success. I also looked through all of the Twin Falls transcribed ones. I'd suggest clicking on the Recorder/Submitter's names, probably Chris Storey, and email. Ask if there are any other cemteries in the area yet untranscribed or where they could be buried. She might even look for the obit of Ethel.
Hove-Robertson Funeral Chapel. 208-324-4555
Farnsworth Mortuary. 208-324-7777
About all I can do.