I added sources to various Turnbow profiles, and created a few more.
Benjamin Riley Turnbow has a Washington death certificate saying he was the son of Steven Turnbow and (unstated) Klapp. He was definitely the son of Turnbow-122 and Clapp-1243. His branch of the family virtually disappears from the records after the 1850 Census in Kentucky until 1900, when they pop up in Whitman County, Washington.
Turnbow-125 has the same spouse, and two different sons. One of them, Isaac P Turnbow, also died in Washington, but before they recorded deaths. I have not found any documents tying either Isaac or TJ Turnbow to Steven - no BMD records or Census records with them in the same home. They might exist, but I didn't find them.
There are references to LDS church records indicating that members of this family were early converts. You can see a description on TJ's FindaGrave memorial, and at Ancestry. I don't know whether those records link the parents, but that would certainly merit further exploration.
Turnbow-122 and -125 might be the same person, or maybe not. Turnbow-125 and Clapp-1243 may or may not be the parents of Isaac and TJ. The sources on the profiles are weak in that area.
Robert, I understand your reluctance to approve the merge without stronger proof. Hope that helps.