I found the Curl family in 1880 in Taylor, Sullivan, Missouri.
Alexander Curl, b. PA, 52, farmer.
Sarah, wife, b. PA, 48.
William L., b. IL, 21, helps on farm.
James, b. IL, 19, helps on farm.
Barnet E., b. IL, 17, helps on farm.
May, b. IL, 14.
Cephes, son, b. MO, 12, helps on farm.
Belle, b. MO, 9.
In 1900 some of the family was living in Taylor.
Cephus Curl, head household, b. MO July 1868, single, farmer.
Alex S. father, b. PA April 1828, widower.
Elizabeth, sister, b. MO Oct 1870 widow [I think this is a mistake], housekeeper, single.
Jim Nilson, farm laborer.
In 1920 Elizabeth and John Nelson were living in Lowe, Kay, Oklahoma.
John A. Nelson, b. PA, 43, farmer.
Elizabeth B., wife, b. MO, 45.
Ralpha A., b. OK, 13.
Harold C., b. OK, 11.
Robert A., b. OK, 9.
Lillian Belle, b. OK, 3 7/12ths.
I didn't find Elizabeth of John in Idaho. Maybe they moved their after the 1930 Census. The 1940 Census will be released April 2 but who knows when it will be indexed.
I also found the McEwen-Serio 2010 family tree, trees.ancestry.com/tree/20079613/person/974831506. I thought you might want to contact the owner. Most larger libraries have free access to Ancestry.
Elizabeth died in Twin Falls on 4 March 1935. There are two Twin Falls obituary volunteers at freepages.genealogy.rootsweb.ancestry.com/~obitl/volid.html . Choose ONE at a time.
Idaho restricts access to death information for 50years after the death. John doesn't appear on their death index even though it's been 50 years. I'd contact the Clerk of the District (who's also the Auditor & Recorder), twinfallscounty.org/dir/clerk.htm for a copy of his death certificate. You'll find his death date on it and then you can request a copy of his obituary too. Successful Searching!