Joseph Smith Jr's Kevo

Smith was married to about 33 women besides Emma. In the group of Smith's well-documented wives, eleven (33 percent) were 14 to 20 years old when they married him. Nine wives (27 percent) were twenty-one to thirty years old. Eight wives (24 percent) were in Smith's own peer group, ages thirty-one to forty. In the group aged forty-one to fifty, there is a substantial drop off: two wives, or 6 percent, and three (9 percent) in the group aged fifty-one to sixty. Although Smith fathered several children with Emma, no additional offspring from any of the women making a "plural wife" claim has ever been proven, and in fact of the approximately twelve children of these wives that were claimed to have been fathered by Joseph Smith, five so far have been conclusively shown as genetically unrelated, through DNA analysis of living descendants. Work is ongoing to determine paternity or non-paternity of the remaining individuals.

In official church publications, Smith publicly denied such doctrines existed, as did his brother Hyrum. Shortly before his death, Smith made a signed denunciation of Hyram Brown for "preaching polygamy, and other false doctrines" in Michigan, cutting him off from the church and requesting that he come to the next Special Conference. Bushman posits that, during Smith's lifetime, his wife Emma reportedly "vacillated between acceptance and rejection" of the practice, with Emma even attending the marriage of Smith to at least one of his plural wives. However, Emma died denying that her husband ever had any other wives, as did Smith's eldest son Joseph, who stated "I have conscientiously traced statements made by various individuals inculpating my father in this wrongdoing, and in every instance I have failed to find evidence worthy to be called proof." Emma Smith's deathbed testimony stated "no such thing as polygamy, or spiritual wifery, was taught, publicly or privately, before my husband's death, that I have now, or ever had any knowledge of... He had no other wife but me; nor did he to my knowledge ever have." However, one modern commentator has stated that due to Emma's opposition to plural marriage, Smith "moved ahead surreptitiously", resulting in Emma's being unaware of the existence of many of Smith's plural wives. Some degree of Emma's opposition may have been directed at clearing up the aftermath of an incident in which:
John C. Bennett, mayor of Nauvoo and adviser to Joseph Smith, ...used the teaching [of plural marriage] to his own advantage. Capitalizing on rumors and lack of understanding among general Church membership, he taught a doctrine of "spiritual wifery." He and associates sought to have illicit sexual relationships with women by telling them that they were married "spiritually," even if they had never been married formally, and that the Prophet approved the arrangement. The Bennett scandal resulted in his excommunication and the disaffection of several others.
Claims that Smith neither taught nor practiced polygamy were at odds with the official publication by the LDS Church in Utah of the Doctrine and Covenants Section 132 in 1852. Unable to produce the original document, Brigham Young declared that Emma Smith had burned it. To this Emma Smith replied that she had never seen such a document, and added concerning the story that she had destroyed the original: "It is false in all its parts, made out of whole cloth, without any foundation in truth."This document, stating to be a revelation recorded on July 12, 1843 in which Jesus Christ is believed to have revealed through Smith that "a new and an everlasting covenant" of marriage is given, which allowed the practice of plural marriage. It contains numerous Biblical references to and justifications of polygamy, as well as the demand that Smith's wife, Emma, accept all of Smith's plural wives, and warns of damnation if the new covenant is not observed. However, in his personal records, Smith nowhere explicitly mentions plural marriage or the existence of other wives. According to Bushman, Smith's scribe Willard Richards is believed to have recorded Smith's plural marriages in Smith's journal in code. It was only after his death that some, including William Marks and Brigham Young, came forward and publicly claimed that Smith taught and practiced plural marriage.

Evidence exists that at least nine of Joseph Smith's wives were civilly married to other men while being religiously sealed (married) to Joseph Smith. Additionally, sealings took place years after Smith's death by proxy in the 1850s in Utah. Some Smith biographers state that the women Joseph Smith was sealed to but not civilly married to were practicing polyandry (the practice of a woman having more than one husband at one time), however polyandry would require at least an attempt at a legal civil marriage. One writer even claims that, while most of these "polyandrous" marriages were with the first husband's consent, others were done behind the first husband's back. The same writer states Smith used warnings of eternal damnation and promises of eternal rewards to secure consent to his proposals. There is no conclusive evidence as to whether or not Smith had sexual relations with women he was sealed to but not civilly married to.

As of 2007, there are at least twelve early Latter Day Saints who, based on historical documents and circumstantial evidence, have been identified as potential Smith offspring stemming from plural marriages. In 2005 and 2007 studies, a geneticist with the Sorenson Molecular Genealogy Foundation (founded by Mormon billionaire James Sorenson) showed "with 99.9 percent accuracy" that five of these individuals were in fact not Smith's children: Mosiah Hancock (son of Clarissa Reed Hancock), Oliver Buell (son of Prescendia Huntington Buell), Moroni Llewellyn Pratt (son of Mary Ann Frost Pratt), Zebulon Jacobs (son of Zina Diantha Huntington Jacobs Smith), and Orrison Smith (son of Fanny Alger). The remaining seven have yet to be conclusively tested, including Josephine Lyon, for whom current DNA testing cannot provide conclusive evidence either way. Lyon's mother, Sylvia Sessions Lyon, left her daughter a deathbed affidavit telling her she was Smith's daughter.