Masaji, Rustom Irani, was Meher Baba's uncle by marriage: his wife Piroja, known as Pila Masi, was the sister of Baba's mother Shireen. Within the family he was called Rustom Masa, and Meher Baba Travels records that he was also nicknamed "Uncle Fish". He was born in 1867. He and Pila Masi had two children who grew up, Aspandiar (Pendu) and Naja, and two others, Gustad and Mehera, who died young. When Merwan was at Deccan College, his drama troupe rehearsed at their home on Sachapir Street in Poona, and Merwan and his friends often played cricket in their large compound.
After Pila Masi died in 1917, Masaji moved from Poona to Ahmednagar, where he worked as a clerk at a liquor store, and his children went to live with their aunt Dowla Masi. When Merwan began gathering his first disciples in Poona in 1922, his uncle brought him his dinner, and at Manzil-e-Meem in Bombay Masaji cooked for the Muslims, Parsis and Iranis among the men, using pure ghee so generously that no one missed meat. He was one of the fourteen men who stayed with Baba at Arangaon in 1923, and he surrendered both his children, Naja and Pendu, to Baba's service.
For the next two decades Masaji did whatever work Baba gave him. He was the cook for most of the mandali, at times a night watchman near Baba, and in Toka in 1928, since the ashram had no sweeper, he cleaned the women's toilets as he had done at Meherabad. In December 1924 he was the only companion on Baba's journey to Belgaum. He had a quick temper but was also a practical joker with a great sense of humour, a strong and fierce man who followed Baba with all his heart.
His love for Baba showed in small ways. On a train journey from Lahore in 1929, when Baba had not eaten for two days, Masaji refused his own food. Asked why, he said, "You have taken nothing for the past two days and again today you are not eating. I do not have any appetite when you go hungry." Baba held this up to the others as an example to be followed.
In December 1944, at 77, Masaji went to Poona to hire cooking vessels for the public celebration of Mehera's birthday. He returned to Meherabad on 18 December with a truckload of supplies, weakened by the journey in the open truck in the hot sun. The next afternoon, 19 December, he was found dead on his bed of heart failure. Baba came from Pimpalgaon, touched the body, helped carry the coffin and was the first to throw earth into the grave. Four days later Baba had the foundation of the Memorial Tower to his departed disciples laid on Masaji's tomb, together with the bedding of Chanji, calling him "my loved Masaji". Meher Baba Travels gives the date of death as 18 December 1944; Lord Meher places it on the 19th.