Mani Irani was Meher Baba's only surviving sister, the youngest of nine children born to Sheriar and Shireen Irani, three of whom died in childhood. When Mani was born on December 15, 1918, her brother Merwan—who would become known as Meher Baba—was already twenty-four years old and under the guidance of the Perfect Master Upasni Maharaj at Sakori. By the time Mani was old enough to understand, her famous brother was already attracting disciples of his own at Meherabad.

From her earliest years, Mani longed to live with her brother and be his disciple. She wrote persistently to him, pleading to be allowed to join him at the ashram. Their mother Shireen, however, wanted to keep her only daughter at home, all the more after their father Sheriar died in 1932 and she needed a family member with her in Poona. Baba resolved this by having his brother Beheram marry and stay with their mother, which freed Mani to join him. In September 1932, at the age of only thirteen, Mani joined Baba's women mandali in the ashram at Nasik as a full resident disciple.

Meher Baba is said to have described Mani as His 'second closest woman disciple' after Mehera Irani, and as His 'spiritual sister.' This distinction—being both His blood sister and His spiritual sister—gave Mani a unique perspective on Baba that she would share with the world through her writings and talks.

Mani was one of only four women chosen to accompany Baba during His extraordinary 'New Life' phase, beginning in October 1949. During this period of complete renunciation, Baba and His companions wandered as spiritual vagrants across India, begging for food and shelter, with no possessions and no certainty of tomorrow. Mani's participation in this rigorous phase testified to her spiritual strength and her complete surrender to her brother's will.

Mani was one of the ten original trustees of the Avatar Meher Baba Trust (the Avatar Meher Baba Perpetual Public Charitable Trust), which Baba registered at Meherabad on 6 April 1959 to care for his physical and spiritual legacy, and she later served as its Chairman. After Baba's physical passing in 1969 she also became one of the primary sources of information about Baba's life and work, welcoming pilgrims at Meherazad and sharing countless stories of life with her divine brother.

Mani's literary contributions to Baba's legacy are significant. Her '82 Family Letters' chronicles Baba's activities from 1956 to 1969 through intimate correspondence with Baba lovers worldwide. 'God-Brother: Stories from My Childhood with Meher Baba' offers precious glimpses of their family life and Baba's early years. 'Dreaming of The Beloved' shares her dreams and experiences. She also contributed to 'Tales from the New Life with Meher Baba' alongside Eruch, Mehera, and Meheru.

Mani passed away on August 19, 1996, at Meherazad. By Meher Baba's directive given during His lifetime, her remains are buried adjacent to His Samadhi at Meherabad—an honor reflecting her unique position as both His blood sister and His spiritual sister.