portuguese were the first europeans to settle in kenya,had their base at fort jesus,mombasa.The arabs,persians(refer to themselves as shirazi"s,in east africa),and turks led by Mir Ali Bey had settled earlier.
The famous Maasai conquered the interior of kenya in the 1700s.
The original inhabitants of kenya,some bushmen tribes,were assimilated or driven to extinction by the current ïnhabitants.hence there is no "real" or "pure" kenyan, its a community of immigrants,each arriving at its own time.
All kenyans apply for citizenship at 18,and get an ID Card.A kenyan birth certificate is not considered a proof or guarantee to citizenship even to africans.
Up to about 5 years ago only whites,asians,and people not of kenyan african background could be allowed IDs registered in Nairobi.