I looked further into the descendant of Oscar's sister Harriet and her husband Alexander McGinnis. They had one grandson, Walter Raymond, who we had lost track of after 1900 when he was living with Harriet on the family farm. Here is some more detail about Walter's life.
In 1918, Walter registered for the World War I Draft in Omaha, Nebraska. He listed his wife as "Nellie" and their address as 110 Golden. His occupation was Refrigeration Engineer for the Pilsbury-Becker Engineering Company with offices in the Central National Bank Building. He listed his height and weight as medium and said he had blue eyes and red hair.
In the 1919 Tulsa City Directory, Walter is now Manager of the same engineering company and his wife is "Nellie" again.
In the 1929 Houston City Directory, Walter is listed as Vice-President of Marine Service, Inc. living at 3812 Austin Street Apt 3. with his wife "Ellen".
In the 1930 Census, he is living with his wife now listed as "Helen" who is 40 years old and who was born in New Mexico. They also have two 23 year old roomers living with them, Nora Mae Clements and Alpha Barnes.
It also appears that Walter's 1952 death was big news big news back in Ohio. I discovered his death was on page 1 of the Coshocton Tribune. I suspect that his mother Bianca stayed in the Coshocton area and he visited regularly. I have sent away for a copy of the article. This should provide any information about his children, if any, and answer the question of his wife's correct name.
I obtained this article and can add this last note. The article described the death of a famous son of Coshocton. He was well known there because his wife's family continued to live in the area. His wife had died before him and it listed no children as surviving him. Apparently, this was the end of Harriet Langford's line.