Her first husband was Nathaniel Alden, whom she married October 1, 1691 at Boston. They had five children: Mary, Nathaniel, Hepzibah, Phillips, and Elizabeth. After he died, she married John Mortimore.
The History of the Town of Duxbuy, Massachusetts with Genealogical Registers shows that
"8. Nathaniel, (s. of 2,) Boston; d. a. 1702, leaving an estate of £86; m. Hepzibah Mountjoy, Oct. 1, 1691; she m. 2d, John Mortemore, June 8, 1703. He had Mary, Aug. 20, 1692; Nathaniel, Aug. 6, 1694 (19); Elizabeth; Hepzibah, m. Nathaniel Hayward, April 28, 1718 ; Philip, Dec. 31, 1698."
↑ Ancestry.com. U.S., New England Marriages Prior to 1700 [database on-line]. Provo, UT, USA: Ancestry.com Operations Inc, 2012.
↑ Ancestry.com. Massachusetts, Town and Vital Records, 1620-1988 [database on-line]. Provo, UT, USA: Ancestry.com Operations, Inc., 2011.
↑ Ancestry.com. U.S.,History of the Town of Duxbury, Massachusetts with Genealogical Registers[database on-line]. Provo, UT, USA: Ancestry.com Operations Inc, 2012.
Source: Woodworth-Barnes, Esther Littleford and Williams, Alicia Crane, Mayflower Families through Five Generations, Vol 16 Part 1 of 3, John Alden, Boston, Mass.: General Society of Mayflower Descendants, 2002. Pages 27, 39.
Source: World Family Tree Vol. 8, Ed. 1, Brøderbund Software, Inc., 1997, Media Family Archive CD
Source: Information was taken from the Alden Kindred website 
No more info is currently available for Hepzibah Mountjoy. Can you add to her biography?