Graduate of University of California at Berkeley, and graduate of Harvard University Law School. Listed as Who's Who in California Attorney's. Leon was an amazingly smart man and exceptional scholar. He argued cases before the Supreme Court. He spoke several languages. He grew up speaking French, then learned Dutch when the family went to their estate in Holland for a year and a half, then English when they came to California and Latin, to their estate 'The Grove' in Oakland, CA.,

Leon married at Oakland, Alameda Co., California, Edith Eleanor Goodfellow, daughter of William Scott Goodfellow and Alice Annott. During WWI, Leon was a Lieutenant stationed in Texas as a flying instructor. Leon and Edith suffered the loss of their young daughter, Leontine de Fremery, at age ten years.

Leon was a widely known yachtsman and one of the founders of the St. Francis Yacht Club in San Francisco. He owned several yachts, but two of them were important. "The Water Witch" was his first larger racing sail boat, and later he had built, to his exact specifications, in Maryland, the "Osprey" which was his last racing boat. He won so many races it is hard to keep count. He and his wife, Edith, traveled all over the world and sailed everywhere. When they were in their 70s, they sailed inland to Illinois, via several different routes, then to Chicago, down the Mississippi, on towards the Caribbean. They were an amazing team together.

Leon was the son of James Leon de Fremery, and Wilhelmina Suermondt. His Brothers were, Adolph Edward de Fremery; Paul William de Fremery; James de Fremery and sister, Virginie Elinor de Fremery, who married Arne Knut Bours Hoisholt who died in WWI in France. He was the son of Dr. Andrew William Hoisholt and Frederica Bours. She married 2nd Chester Lawerance Gorrill.