Question: Why Do Mormons Research Their Ancestors
Members of the Church of Jesus Christ of Latter-day Saints, usually referred to as Mormons, place great emphasis on genealogical research. This is because their Church doctrine states that "saving ordinances" (including baptism, confirmation, endowment, and sealing-marriage) must be made available to every individual who has ever lived. To make these ordinances available to people who did not have the opportunity while living, Mormons identify their ancestors and arrange for baptism and other ordinances to be performed for them by proxythat is, with a living person standing in for the deceased personin a temple. Often referred to as temple work, this search for ancestors is an important part of the Mormon faith.
For further reading:
Genealogy According to Mormons
LDS FAQ - Genealogy, Family History