WILMINGTON, Del (Reuters) - F. Scott Fitzgerald observed that the rich are different, but that does not mean an heiress can adopt her 65-year-old ex-husband to increase her family’s claim to a billion dollar inheritance.

Delaware’s Supreme Court ruled on Tuesday that the unconventional adoption did not entitle the man to inherit a share of the Gore-Tex waterproof fabric fortune.

Heirs to the founders of W.L. Gore & Associates Inc of Newark, Delaware, have fought for years over how to divide their stake in the privately held company, which has $3 billion in annual revenue.

Their battle landed in court over the question of how the late Wilbert L. Gore, who founded the company in his basement in 1958, and his late wife, Vieve, intended to divide their fortune.

At the center of the dispute was the adoption nearly a decade ago by Susan Gore, one of Wilbert’s five children, of her ex-husband, Jan Otto.

According to the court’s opinion, Susan Gore and her son Nathan Otto began considering the adoption to even out the potential distribution from a family trust, which was meant to divide 26,500 Gore shares.

But because Susan Gore and Jan Otto had three children, while each of her four siblings had four, Susan’s children stood to inherit fewer shares, according to the opinion. Eventually, the court said in its decision, she decided to adopt her ex-husband, who initially assured her he wanted to be her son merely to benefit their children.

Susan Gore went to a Wyoming court and secretly adopted Jan Otto in 2003, when he was 65. A year later, Jan Otto had a change of heart and decided to keep the potential distribution from the trust for himself, according to the court ruling.

While Susan was considering whether to “un-adopt” her ex-husband in 2005, according to the opinion, her mother Vieve Gore died, releasing the trust assets and setting in motion the legal wrangling that led to the court’s ruling.

“The fact that Susan kept this adoption secret until Vieve died further evidences that Susan and the Otto grandchildren knew that they were acting to thwart Vieve’s intentions,” Chief Justice Myron Steele wrote in the 37-page opinion.

Attorneys for Susan Gore, Jan Otto, Nathan Otto and Susan Gore’s siblings did not immediately return calls seeking comment. W.L. Gore & Associates spokeswoman Susan Crow did not immediately return an e-mail seeking comment.