At least date of birth, date of death - if it has happened. Name of spouse, their parents, spouse's date of birth/death. Children - same as above.
Nicki Dianne Harper born Nov 22, 1943 Minneapolis, Hennepin County, MN. Married Jerome Peter Muggli born July 7, 1939 St. Cloud, Stearns County, MN to Anna Fleck Muggli and Isadore Muggli. Divorced August 1977 and returned to maiden name. Living. One child: Anjanette Cecelia born Mar 19, 1973. Anjanette changed her last name to Harper on her 18th birthday.
In addition - any other information you want passed on.
If people do not want this information given to people not in the family, they should indicate. Most programs let you exclude the information about living people automatically. But we would want to keep our own record for family use, it seems to me.