@Kratos/cmk @Magigi and @User, some research you've done there....making some sense

This is possible. The prominent Waiyaki family claims its patriarch was a Maasai.

The Gikuyu community is full of such cases of assimilation. We have so many Kamau and Njoroge Maasai, Dorobo and Kambas within this community.

Fake theory, on one part he is a Nandi on the other a Kipsigis.

But the Kenyatta family is also known to have Maasai links.

Everything is possible. Figure out this;

The Abatoro people in Western Uganda Claim that in 1880s when their King was exiled in Kenya after resisting the colonialists stayed in an area around Nairobi (Thogoto/Gatundu etc).The king befriended a girl and after some landings the girl became pregnant and Kamau Johnstone born 9 months later.To this date,The Toro kingdom believe Kenyatta is the son of their King.

On another note,The kambas are sons and daughters of Wamuyu,Gikuyu and Mumbi's 10th daughter normally referred to as kenda muiyuru.
Wamuyu liked had higher affinity for landing gear and when Gikuyu was praying for Ngai (Mwene Nyaga)to send men to marry his daughters,Wamuyu was already pregnant ( believed to be from a maasai moran who was taking care of his fathers cattle).
This infuriated Gikuyu and chased away his daughter who went to nearby land with the maasai moran.
This is how Kambas came about and their affinity for landing gears still a respected affair to date.

The Kikuyu is an amalgamation of many tribes eg. the extinct: the Ngumba, the Athi, the Dorobo etc that were basically hunter-gatherer communities. Others include the Maa speaking people, tharaka, mbeere, chuka, embu, kamba.
Kikuyu is a language, not DNA.