The Rev. Moon and wife Hak Ja Han have 10 surviving children, and in recent years, the aging Moon had been handing power on the church's religious, charitable and business entities to them.
But there have been reports of family rifts. One son sued his mother's missionary group in 2011, demanding the return of more than $22 million he claimed was sent without his consent from a company he runs to her charity. His mother's group eventually returned the money after court mediation.
Church officials said the son, known as Preston, is no longer in charge of any church operations.
Moon's death could expose further rifts within the church, said Kim Heung-soo, who teaches the history of Christianity at Mokwon University in the central city of Daejeon.
"There is a high possibility that internal discord will deepen," Kim said.
The church has amassed dozens of businesses in the United States, South Korea and even North Korea, including hotels, a ski resort, sports teams, schools, universities and hospitals.
One expert said the church's business prospects appear brighter than its religious future. Tark Ji-il, a professor of religion at Busan Presbyterian University, described the church not as a religious organization but as a corporation made up of people with similar religious beliefs.
The church won't give details about how much its businesses are worth, other than to describe them as part of a "multibillion-dollar" empire.
Many new religious movements collapse after their founders die, but Tark said the Unification Church would likely survive. But its success as a religious entity will depend on how it smoothly it resolves any family feuds and how well Moon's offspring rise to fill their father's charismatic role, he said.
The Unification Church claims three million followers, though ex-members and critics put the number at no more than 100,000.
Church officials said that Moon's funeral would take place Sept. 15 after a 13-day mourning period, with a massive new sports and cultural center built recently on the church's sprawling campus accepting mourners starting Thursday.