Roy Henry Cullen, the grandson of legendary oilman Hugh Roy Cullen and a member of Houston's most prominent philanthropic family, died Friday at his River Oaks home. The cause of death has not been officially determined. (Update 04/07: The Harris County Medical Examiner's Office has ruled that the death was a suicide.)

Cullen was 84.

Born on Oct. 29, 1929, the oldest child of Roy Gustav Cullen and Katherine Thompson Cullen, Cullen later joke that he was born on the day of the great stock market crash. After graduating from Lamar High School and attending Rensselaer Polytechnic Institute in Troy, N.Y., where he studied engineering, Cullen learned the "oil business" from his grandfather, and, with other family members, discovered and developed oil fields operated by Quintana Petroleum Company. He served as an officer and director of Quintana for many years.

Cullen was one of the original board members of Cullen Bank and continued to serve on the board after its merger with Frost Bank in 1977.

Among his many charitable interests, Cullen, who chaired the board of the Cullen Foundation from 1998 until January of this year, worked actively to raise money and awareness of Parkinson's Disease. Once his daughter, Lillie, was diagnosed with the disease at age 38, he was passionate about helping researchers find a cure. She died in 2004 at age 53.

Cullen is survived by his wife, Mary Garcia Cullen, four children, brother Harry Cullen, sister Cornelia Long, and numerous extended family members.

Geo. H. Lewis & Sons is handling funeral arrangements. Visitation at the funeral home, located at 1010 Bering Drive, will take place on Monday from 5 - 8 p.m. A memorial service will be held at 11 a.m. Tuesday at Church of St. John The Divine, 2450 River Oaks Boulevard, following a private burial at Forest Park Lawndale Cemetery.

In lieu of usual remembrances, the family has asked that contributions be made to Houston Area Parkinson Society, 1475 W. Gray St., Houston, TX, 77019; or the Museum of Fine Arts, Houston, 1001 Bissonnet St., Houston, TX, 77005.