Always Time To Die by Elizabeth Lowell
Carly May is a genealogist who is invited to New Mexico to chart a family tree for the Quantrell family. The Quantrell family has intermingled with the Castillo family for centuries. But now the powerful Senator has died and Miss Winnifred Quantrell wants a record of the family. But there have been some nasty people in the family and someone wants the skeletons left in the closet.