Shirley and Sally Louise

Just when I thought I had finished with the Ethel McCann archive, another picture turns up. "This is Shirley and cute Sally Louise. It doesn't do Shirley justice really - she has lovely colouring auburn hair and blue eyed - she is Scottish descent (nee Hamilton)" Is Sally Ethel's granddaughter and if so where does the name Jarvis come from? Or possibly Shirley was married to Bob's son by a previous marriage.

*Update, July 2016*
My speculation that Sally is related to Ethel and/or Bob appears wide of the mark. But I have found some more information.
On 8 October 1937, Shirley Elizabeth Hamilton of 23 S. Catalina St. Los Angeles married Arthur Tedcastle Jarvis Jr of 817 North Bedford Drive, Beverly Hills. Witnesses were Samuel A. Street and Sally Louise Hamilton, Shirley's younger sister. The marriage was solemnised by Thomas J. O'Sullivan, catholic priest, of 5801 Carlton Way, Hollywood.
https://familysearch.org/ark:/61903/1:1:K8VM-K32

The 1940 census finds Arthur, Shirley, daughter Sally (then 0 years old) and Arthur's parents at 817 Whittier Drive, Beverly Hills (now 90210)

For more about Sally, see http://mackiegenealogy.blogspot.co.uk/2008/02/sally-louise-jarvis.html

More about Shirley
Shirley was born on 16 January 1914 in Baxter, Jasper, Iowa. Her parents were (Dr.) William Franklin Hamilton, born in State Center, Iowa and Shirley Marks MacLennan, born in Clleveland, Ohio.
https://familysearch.org/ark:/61903/1:1:V46J-WTK

More about Arthur
Various records give his occupation as real estate.
Arthur was born on 22 March 1914 in Nashville, Tennessee. His parents were Arthur Tedcastle Jarvis, born in Virginia c. 1883 and Louise O'Keefe, born in Nashville c. 1887.
There is a good match in United States World War II Army Enlistment Records with Arthur T. Jarvis, born 1914 in Tennessee. He enlisted as a Private in the Air Corps on 14 July 1942 in Des Moines, Iowa
https://familysearch.org/ark:/61903/1:1:K85J-N9T
Arthur remarried on 27 November 1946 in Los Angeles to Lura Joy White, 23. He was still at 817 North Bedford Drive. Lura's parents are given as Lewis A. White and "Ocy L. Jones" but the original image is indistinct. Best match I births register for Lura is Lura J White, 5 March 1923, Los Angeles.
His birth date was 2 July 1914 and died on 2 July 2004 in Beverly Hills 90212.
https://familysearch.org/ark:/61903/1:1:J5FC-VZL
He was buried in  Rose Hills Memorial Park, Whittier, Los Angeles, California