He previously held different public service positions, including District Officer and the Assistant Secretary in the Ministry of Home Affairs. He also served as the Personal Assistant to ex-president Uhuru Kenyatta, when he was the Minister for Local Government between 2001 and 2002.
While settling on Gachagua as his deputy in July, William Ruto said the then-Mathira MP's grassroots mobilisation skills and understanding of Kenyans' challenges made him a perfect fit for the role.
Gachagua holds a Bachelor of Arts Degree in Political Science and Literature from the University of Nairobi. He graduated in 1988.
A tough talker, well-moneyed, and great campaigner, it would be interesting to see how Gachagua's tenure as deputy president pans out.
In his speech on Tuesday, shortly after his swearing-in, he said it would be difficult to fit in the shoes of William Ruto, whom he described as a hard-working deputy president under Uhuru Kenyatta's reign.
Davis Chirchir
He's described as an IT expert par excellence.
The 61-year-old sprang to the public limelight in 2013, when Uhuru Kenyatta appointed him as the Cabinet Secretary (CS) for Energy and Petroleum.
In March 2015, President Kenyatta suspended Davis Chirchir and three other Cabinet Secretaries after an EACC report recommended their suspension to pave way for investigations into alleged impropriety.
The other three were Felix Koskei (Agriculture), Michael Kamau (Transport) and Kazungu Kambi (Labour).
There is speculation that Chirchir was Ruto's pick for the Energy CS position, when Kenyatta and Ruto had allegedly struck a deal to share Cabinet slots on a half-to-half basis.
Chirchir holds a Master of Business Administration Degree from the Royal Holloway University in London, the United Kingdom.
He also holds a Bachelor of Science Degree in Computer Science and Physics from the University of Nairobi.
He previously worked in several mid-level positions at the Kenya Posta before rising up the ranks in the corporate department.
Former President Uhuru Kenyatta appointed him the Chief Administrative Secretary (CAS) at the Ministry of Foreign Affairs on January 26, 2018. In February 2022, he resigned from the post to serve as Ruto's diaspora chief campaigns officer.
There are reports that he is angling for the Foreign Affairs Cabinet Secretary (CS) post in President Ruto's government.
Ruto, in his maiden speech as President on Tuesday, said he'll form a Ministry of Diaspora Welfare. Should Namwamba miss out on the Foreign Affairs post, he could secure landing in the newly-created diaspora ministry.
Korir Sing'oei
The fourth person pictured with Ruto during the Tuesday signing of the Executive Order on the Appointment of Judges was Korir Sing'oei.
Sing'oei, until Tuesday, served as the Legal Advisor at the Executive Office of the Deputy President, where he was also the Head of Law and Policy.
Sing'oei is an advocate of the High Court of Kenya.
He holds a Master of International Law and Economics Degree from the University of Minnesota in USA. He also holds a second Master's Degree in Comparative Human Rights Systems from the University of Pretoria, South Africa.
He pursued an undergraduate Degree in Law from the University of Nairobi, where he graduated in 1998. He's also a holder of a Diploma in Legal Practice from the Kenya School of Law.
He's served as a Senior Conflict Management and Rule of Law specialist at the United States Agency for International Development (USAID). Besides that, between 2002 and 2006, he was the Executive Director of the Center for Minority Rights Development.
Sing'oei has also had a stint as Law lecturer at the Kenyatta University in Nairobi.