I presume you've seen on the CA birth database the boy born in LA County on your day with the names Martin and Wiand. Another boy is listed with Martin as both the surname and mother's name -- probably a duplicate listing.
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The name Wiand is not very common, so have you looked up all the men with that last name in CA? With some cross-referencing on the various people search sites, you can figure out their approximate ages. Perhaps it wouldn't hurt to send a letter to all the possible fathers, or even send letters to all Wiands (male and female) in case some family member would have some knowledge. You might also try searching for Wiands on classmate sites in the Granada Hills area (there are also a number of other cities in the San Fernando Valley surrounding Granada Hills so don't limit yourself to just GH). Every city did not have its own hospital. Do you have any idea how old your bparents were? If you could guess what year your bmom graduated from high school, you could contact any girl with the maiden name Martin at the right age.
Sorry I don't have better advice. I'm not sure what you'd have to do to get your original birth certificate. Best of wishes.