Fielding was baptized into the Church of the Latter Day Saints on May 21, 1836 by Parley P. Pratt. He was ordained a teacher in the summer of 1836 and a priest in May 1837. He then moved his family to Kirtland, Ohio to join the general body of the church in May 1837. HIs sister Mercy Fielding, born 15 June 1807, married fellow Latter-day Saint Robert Blashel Thompson, who served as a faithful missionary to Canada and later became associate editor of Times and Seasons. He died of consumption in 1841. In 1837, Mary Fielding met and married widower Hyrum Smith, Patriarch of The Church of Jesus Christ of Latter-day Saints and brother to the prophet Joseph Smith. She became stepmother to his six children by his first wife and on 13 November 1838 bore him a son, Joseph F. Smith, and later a daughter Martha Ann. Joseph F. Smith was to serve as counsellor to four prophets before becoming the sixth President of the Church in 1901, at the age of 62. His own child, Hyrum and Mary’s grandson, Joseph Fielding Smith, born 19 July 1876, became the 10th President of the Church in 1970, at the age of 93. Another grandson, Hyrum Mack Smith, was ordained an apostle in 1901 and his grandson, M Russell Ballard is a serving apostle, called in 1985.