George Herbert Walker III, a St. Louis businessman and philanthropist who was the cousin of two presidents and served as U.S. ambassador to Hungary, died Jan. 18 at a hospice center in Creve Coeur, Mo. He was 88.

His wife, Carol Walker, told the St. Louis Post-Dispatch that the cause was complications from a stroke.

Mr. Walker, known as “Bert,” was born in St. Louis on March 16, 1931, and grew up in Greenwich, Conn. He was a 1953 graduate of Yale and received a law degree from Harvard in 1956.

After serving in the Air Force, he moved to St. Louis in 1958 to work for the financial services company founded by a grandfather. Mr. Walker later served as president and chief executive for Stifel, Nicolaus & Co., a brokerage and investment banking firm.

In 1992, as George H.W. Bush sought a second term as president, Mr. Walker tried his own hand at politics, seeking the Republican nomination for a suburban St. Louis congressional district. Both bids were unsuccessful.

Mr. Walker remained active in Republican politics, including successful presidential campaigns for another cousin, George W. Bush, in 2000 and 2004. George W. Bush appointed Mr. Walker as ambassador to Hungary in 2003. He served in that role until 2006.

Mr. Walker was active in St. Louis civic organizations. He was a trustee of Webster University for 42 years, and the business school was named for Mr. Walker after a $10 million donation in 2005.

Survivors include his wife, the former Carol Banta; two siblings; and many children, stepchildren and grandchildren.