continue much of that charitable work

continue much of that charitable work opponents, who label it a death tax, say it is unfairdoomen because it taxes the same income twice — once when it is earned and again when it is passed on to heirs.

Mr. Duncan’s eldest daughter, Randa Duncan Williams, is serving as executor of the estate and is a voting member of the family trust that will now control her father’s interest in Enterprise GP Holdings.

Should the family trust sell these inherited shares, capital gains taxes would presumably be owed on the difference between Mr. Duncan’s original cost, which could be quite low, and their market value when sold. Capital gains taxes are capped at 15 percent.

Ms. Williams, who has served as a director and general partner at the family’s energy businesses for years, was deeply involved in her father’s philanthropic efforts and is expected to continue much of that charitable work.

During his life, Mr. Duncan contributed to a wide assortment of wildlife foundations and community institutions like the Houston Zoo and Houston Museum of Science, and an assortment of medical institutions. The various medical centers at Baylor College of Medicine received more than $250 million from Mr. Duncan and his wife, with more than $100 million used to found the Dan L. Duncan Cancer Center.

Mr. Duncan’s will designates a handful of nonprofit groups and charitable foundations that will receive donations, all of which would have been tax-exempt even in years when the estate tax was in effect.

An avid big game hunter — Mr. Duncan has more than 500 entries in the Safari Club International record book for killing animals including polar bears, rhinoceroses, bighorn sheep, doomenlions and elephants — he made a $1 million donation in his will to the Shikar Safari Club International Foundation.