[2] Among his siblings was Mason Fay Prosser, an attorney in Honolulu, Hawaii.
[2] Prosser began his career with Equitable Life Assurance Society of the United States.
[2] Together, they lived in Englewood, New Jersey and in Woods Hole, Massachusetts (on Cape Cod),[6] were the parents of:[1] He was a member of the Union League Club and the University Club of New York.
[1] His funeral was held at the First Presbyterian Church of Englewood,[16] and more than 1,000 persons attended with more than 40 friends and associates noted as honorary pallbearers.
[18] Through his eldest daughter, he was a grandfather of Prosser Gifford, a Director for the Office of Scholarly Programs in the Library of Congress who wrote a series on British and German colonialism in Africa.