Brigham Young (aged 42) marriage to Augusta Adams (1802-1886) (aged 40) married to non-Mormon Henry Cobb (divorced in 1847) Young later married her son's ex-wife, Mary Van Cott Cobb (No. 51). Grandmother of architect Henry Ives Cobb.
Brigham Young (aged 42) marriage to Harriet Elizabeth Cook (1824-1898) (aged 19) first marriage 1 child.
Joseph has Brigham Young seal him to Brigham's fifty-six-year-old twice-widowed sister, Fanny Young Carr Murray. She is the stepmother of Heber C. Kimball's wife Vilate and apparently Joseph's last-married plural wife.
Fanny was already married to a living husband, Roswell Murray. Brigham Young reported the marriage of his sister to Joseph Smith in the Journal of Discourse:
"Now, don't talk to me; when I get into the celestial kingdom, if I ever get there, I shall request the privilege of being a ministering angel; that is the labor I wish to perform. I don't want any companion in that world; and if the Lord will make me a ministering angel, it is all I want." Joseph replied, "Sister, you talk very foolishly, you do not know what you will want." and then turned to Brigham, "Here, Brother Brigham, you seal this lady to me." Brigham said that Fanny submitted to Joseph's impromptu proposal and he "sealed her to him."
[Wikipedia, List of Brigham Young's Wives, http://en.wikipedia.org/wiki/List_of_Brigham_Young%27s_wives;Joseph Smith Polygamy Timeline, http://www.i4m.com/think/polygamy/JS_Polygamy_Timeline.htm;Journal of Discourses, vol. 16, pg. 166-167)]