Speaking at Brigham Young University, Mary Elizabeth Lightner, plural wife of Joseph Smith says, "I went forward and was sealed to him [Joseph Smith]. Brigham Young performed the sealing, and Heber C. Kimball the blessing. I know he [Joseph] had six wives and I have known some of them from childhood up. I knew he had three children. They told me. I think two are living today but they are not known as his children as they go by other names."
[On This Day in Mormon History, http://onthisdayinmormonhistory.blogspot.com]