Hi Jenevia, The information you are looking for all happened after 1930 therefore, there are no clues available in the Censuses.
I looked for Cecil in Ancestry and FamilySearch but didn't find his or their marriage in either place. I assume they were married about 1936 and maybe in Florida. You can post your request for that piece of information on the Gulf County Florida Message Board.
I'd contact a volunteer at Random Acts Genealogical Kindness, raogk.org who will look up marriage certificates. Go to raogk.org Choose California Choose J thru L Scroll down to Los Angeles Co. and choose Kathryn. She will look for Mattie and Sidney's marriage certificate and find the information for Sidney. However, not much info might be there because of when they were married. The very early Marriage Licenses have a lot of info about the bride and groom. The later ones don't.
Do you have a copy of Mattie's obituary? It might contain more information. There is an obituary volunteer for Riverside Co. on RAOGK too. Successful Searching!