E Pierce Marshall, 67, died of an "extremely aggressive infection", family spokesman David Margulies wrote in a statement, the Houston Chronicle reported today.
Marshall’s death comes before his long-running battle with Smith reached a conclusion.
The fight went all the way to the US Supreme Court, which last month sided with the ex-stripper, saying the matter was not the exclusive jurisdiction of a Texas court that had ruled in favor of the younger Marshall.
Smith met J Howard Marshall II at the club where she worked as a topless dancer when she was 26 and he was 89.
He died 14 months after they wed. Smith claimed Marshall verbally promised her half of his estate, worth millions, but E Pierce Marshall claimed to be the only beneficiary.
The Supreme Court ruling gave Smith another chance to collect some of her dead husband’s riches.
CNN also reported on Marshall’s death here.