Later he became the leader of the Forty Group, an organisation supporting the Kenya African Union (KAU).
His brother, Joseph Kiiru Mirugi, died in 2009 in Mahiga, Othaya and his wife, Muthoni wa Mathenge, is still alive and resides in Mweiga, Nyeri.
One prevailing conspiracy theory is that he was killed in his power rivalry with Kimathi, who then made up the story that Mathenge had gone to Ethiopia to seek assistance from Haile Selassie.
[5] On May 30, 2003 a man believed to be Stanley Mathenge, living in Ethiopia, was invited to Kenya by president Mwai Kibaki and was given a hero's welcome by the state.
It was soon revealed that the man was Ato Lemma Ayanu, who himself denied being Mathenge.