James Felix Ndung'u Mithaa was born in 1947 at Wa-Mugo Village, Ngooru Sub-location, Tetu Constituency, Nyeri County. He was the son of the late Mithaa Rebania and the late Phyris Wairima, and a loving brother to Eunice Wambui, Nancy Muthoni Maina, Loise Nyawira, Samuel Nderitu, and the late Jane Susan Wanjiku, Martha Wangui, and Naomi Wanjiru.

Raised as a disciplined and respectful child, he began his education at Miagayuini Primary School and later proceeded to Kimathi Secondary School. He began his career at the District Commissioner's (DC) office, where he served diligently as a public servant for many years until his retirement in 2002.

Ndung'u met his beloved wife Esther Wanjiru Mwihia in 1983, and they married in 1984 in accordance with Kikuyu customs. They were blessed with two children: Gibson Mithaa and Joseph Mwihia. He was a loving father-in-law to Loise Mukami and Joan Wanjeri, and a doting grandfather to Emmanuel Ndung'u, Fredrick Njagi, Eli Rebania, Essie Wanjiru, and Moran Mugo.

A Christian from baptism on 29th August 1959 at PCEA Miagayuini Church by Reverend Mishek Kamwaro, he reaffirmed his faith in 2025 and joined PCEA Kihingo Church, where he remained a member until his passing.

Blessed with good health for many years, he began experiencing breathing difficulties in June 2024 and received treatment at Outspan Hospital, Nyeri. After further admissions at Consolata Hospital Mathari, he peacefully passed away during the night of April 12, 2026, at the age of 79.

He is survived by his loving wife, two children, and five grandchildren.