A jury has rejected a claim by reclusive US billionaire Donald Bren's two grown-up children for $US134 million ($150 million) in retroactive child support.

Jurors deliberated for two hours in a Los Angeles court before siding with the 78-year-old, whose lawyer argued that no family court would have given the children more than the millions he had already paid.

Winner ... Donald Bren Credit:AP

The unusual case was a high-stakes contest between one of the nation's richest men and two adult children he fathered during a 13-year affair with Jennifer McKay Gold. She brought the lawsuit on behalf of her children, Christie Bren, 22, and her brother, David, 18.

Ms Gold, who signed agreements with Donald Bren when the children were born, said they were cheated out of the support to which they were entitled.