“Because we’re all siblings,” she said. “We have to always look out for one another.”

Nothing about Ms. Sinta’s early years predicted how high she would rise.

Born in 1948 in the rural East Javanese town of Jombang, she was the eldest daughter and one of 18 children of a calligrapher father who had one wife. She was educated at a local Islamic boarding school for girls, where she impressed teachers with her religiosity and academic ambition.

Mr. Wahid, a charismatic young teacher at the school whose father was the leader of Nahdlatul Ulama, Indonesia’s largest Muslim organization, fell in love with the outspoken and beautiful young woman, then only 13. He would visit her house after school to play chess with her father, eventually asking for permission to marry his daughter.

But Ms. Sinta told her father she was not interested. “I was too young, and love hadn’t blossomed yet,” she said. It was considered scandalous that a girl from an ordinary family would turn down Mr. Wahid, but her father left the decision to her.

It was the unlikely start of a great romance.

After Mr. Wahid moved to Cairo to study, and struggled in class, Ms. Sinta wrote him: “Mankind shouldn’t always fail in life. If right now you’re failing in your studies, then you shouldn’t also fail in love.”

He took the opening, writing then from Baghdad, where he had moved, to ask her to marry him. This time, she was ready, but because he would not come home from Iraq for three more years, his grandfather represented him at the marriage ceremony.