Gatheca is one of four members of the Kenyatta family who have taunted for the highly competitive position. She is also the immediate former Kiambu Woman Representative.
Apart from Gatheca, Sonko had indicated that he was considering the President's younger brother Muhoho Kenyatta.
Uhuru's nephew Jomo Gecaga and his partner Anne Kiguta, were also included in Sonko's list of promising candidates.
She has also won the support of NASA leader Raila Odinga who has recently made a peace deal with President Kenyatta.
While endorsing her, Odinga said he has known Annah for a long time and her record speaks for itself especially when it comes to promotion of gender equality, economic empowerment and wealth creation.
The former Woman Representative holds a bachelor of arts degree in political from York University of Canada.
She is the daughter to Gatheca Muhoho, who is the younger brother to Mama Ngina Kenyatta.