It appears that Mombasa was part of British Kenya for decades before it was formally ceded to newly independent Kenya in 1963. The British certainly administered it as part of the British East Africa Protectorate, later known as the Kenya Colony, for decades prior to 1963; in fact, Mombasa was the capital of the British East Africa Protectorate and the Kenya Colony. See http://encyclopedia.farlex.com/Mombasa,+Kenya (”Mombasa came under the control of the sultan of Zanzibar in 1840 and was leased to the British in 1895. From 1905 to 1907 it was the capital of the British East Africa Protectorate. In 1920 it became capital of the British Protectorate of Kenya. Mombasa officially belonged to Zanzibar from 1895 to 1963 when it was ceded to the newly independent Kenya.”)
So I have to believe that the birth certificate for someone born in Mombasa in 1961 would say that he was born in Kenya, not in Zanzibar.
Which is not to say that the Kenyan birth certificate isn’t a fake, just that it saying Mombasa, Kenya doesn’t make it a fake.
Now, after having reviewed some more facts, I am going to jump on the "likely fake" bandwagon.
Please see the thread, "Kenya Register of Birth," for my rationale for doing so.
Not to say that I am absolutely, 100%, saying it's a fake, but it looks more suspicious to me.
“So I have to believe that the birth certificate for someone born in Mombasa in 1961 would say that he was born in Kenya, not in Zanzibar.”
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And the Republic of Kenya, at that:
http://www.freerepublic.com/focus/news/2306755/posts?page=809#809