Mrs Michuki died at the Nairobi Hospital Wednesday morning where she was undergoing treatment.
"Very, very painful. Our mother-in law, Mrs Josephine Michuki, died early today at Nairobi hospital," said former Information Mutahi Kagwe on his Facebook page.''Good people, we desperately need your prayers."
Mr Kagwe is a son-in-law of the Michukis. Her death comes months after Mr Michuki passed on. The late minister died in February, aged 80.