JOEL - There's no reason to get too upset. I wouldn't exactly
call it "marriage" in the traditional sense. There was
no marriage license. As far as I know,
there are records of Joseph Smith being "sealed"(like
in the temple ordinance) to a 14 year-old girl named
Helen Mar Kimball, but there is no evidence that
he actually lived with the girl or had any sexual
relations with her (including other women he was
sealed to). This was called "theological polygyny";
or sealing for eternity without earthly cohabitation.
The sealing of Helen Mar Kimball to Joseph was not his
idea, it was her father's insistance that she do this.
According to her:
"My father...taught me the principle of Celestial marrage, & having a great desire to be connected with the Prophet, Joseph, he offered me to him; this I afterwards learned from the Prophet's own mouth...my father introduced to me this principle & asked me if I would be sealed to Joseph." (Helen Mar Whitney, A Woman's View: Helen Mar Whitney's Reminiscences of Early Church History (Provo, Utah: BYU Religious Studies Center, 1999), 482-487.)
Helen continued to live with her parents after the sealing. (Anderson and Faulring, "Compton: In Sacred Loneliness," 80.)
Many early Mormons believed that to ensure their
exaltation in heaven they should be sealed to someone
else who would most likely gain exaltation, such as
the prophet Joseph Smith.
This is something Helen Kimball's father wanted for
her. Joseph was sealed in this way to other women and
even to some men who believed this would assure them
exaltation in heaven.
But these sealings were something that were meant to
have an effect only in the next life.
On a related subject, teenage marriages in the nineteenth century were quite common. We know that later on there were marriages of young girls during Utah’s polygamous years that were performed with the understanding that cohabitation would be postponed until the girl had arrived at a suitable, marriageable age. (Eugene E. Campbell, Establishing Zion: The Mormon Church in the American West 1847-1869 (SLC: Signature Books, 1988), p. 198 note 5.)
Despite how things may seem to us as we read about it 170 years later, we need to have faith that, even though Church leaders were not perfect, they did not do anything that God would not have approved of.