Adele Astaire's father was Catholic; her mother was Lutheran.
Alessandra Garofalo has conducted primary research into the European background and history of Fred Astaire's father, Fritz Austerlitz. This research is the basis for some of the information on the "Porges families Home page" website and Hyde Flipp's article, cited below.
Webpage: "Family of Ester Porges (1804-1869) [and descendant] Fred Astaire (Frederick Austerlitz)" on the "Porges families Home page" website (http://www.porges.net/FamilyTreesBiographies/EsterPorges18041859.html; viewed 29 June 2005):
Austerlitz (b. Prague ca 1830, d. ?): The claim that one branch of the Austerlitz family lived here on the Unterbergsgasse in the old Jewish quarter of Eisenstadt, Austria seems to be a myth. Astaire's grandfather was said to have once lived here, but Fred Astaire's parents were Catholic and Lutheran and he was an Episcopalian all of his adult life.
From: Hyde Flippo, "Fred Astaire (1899-1987) aka Frederick Austerlitz" page on "The German-Hollywood Connection" website (URL: http://www.germanhollywood.com/astaire.html; v. 17 May 2005):
...Fred and his sister were born with the last name Austerlitz and their roots go back to Austria and Alsace... [photo caption:] Fred Astaire's Austrian father was baptized as Friedrich Emanuel Austerlitz in this Catholic church near Linz in 1868. [end caption] ...After his arrival in New York... Fritz Austerlitz made his way west to Omaha, Nebraska. There he met... Johanna (Ann) Geilus. Johanna had been born in Omaha, but her parents... were German-speaking, Lutheran immigrants from East Prussia and Alsace. The 25-year-old Fritz and 16-year-old Johanna were married at the First German Lutheran Church in Omaha on Nov. 17, 1894... Fritz and Ann Austerlitz's first child was a daughter, Adele, born in 1896. On May 10, 1899 Adele's brother Fred came into the world. The two children were destined to be an entertainment team for many years until Adele tired of the show business routine and got married.
Hyde Flippo, author of the Fred Astaire page on The German-Hollywood Connection website, wrote to us (17 May 2005) and pointed out that Fred Astaire (Austerlitz) is "a descendent of an Austrian/Bohemian German-speaking Jewish family originally from Prague. His European relatives were all born Jewish, although Fred's father and the rest of his immediate family converted to Catholicism when they were living in Linz, Austria (where Fred's father, Fritz Austerlitz, was born and baptized)."
From: P.J. Thum, "Biography: Youth" web page on "FredAstaire.net" website (http://www.fredastaire.net/biography/youth.htm; v. 11 May 2005):
Fred Astaire's father Fritz E. Austerlitz (1869-1924) was born Friedrich Emanuel Austerlitz in Linz on September 8, 1868 into a Roman Catholic family... in Vienna, Austria... In Nebraska, he met and became infatuated with Johanna Geilus (1878-1975), a seventeen-year-old girl of Alsatian parentage [who would become Fred Astaire's mother]... While her parents were against the marriage -- especially since he was almost ten years older, Johanna's pregnancy forced them to accept Fritz. Fritz and Johanna were married on Nov. 17, 1894 at the Erste Lutheran Kirche in Omaha by Rev. Freese.
From: Thomas, Astaire: The Man, The Dancer, pages 11-13:
According to family legend, Frederick Austerlitz [Adele and Fred Astaire's father] left Austria as a result of a dispute with his older brother Ernest. Both were officers in the Emperor's army... He arrived in New York in 1895, remaining only briefly after his release from Ellis Island. Friends in Vienna had arranged a job for him in the leather trade in Omaha, Nebraska...
Austerlitz became a popular figure at parties among Omaha's young people. One night he met a pretty girl of Alsatian [a region in France adjacent to Germany] parentage named Ann Gelius, only recently graduated from a Catholic high school. Although there was ten years' difference in their ages, they fell in love and married within a few months. They moved into a wood frame house on North Nineteenth Street, a short distance from downtown Omaha. Their daughter Adele was born September 10, 1897. On May 10, 1899, Ann Austerlitz gave birth to a son, named after his father... [That second child was Fred Astaire.]
[page 13] In 1904, the God-fearing citizens of Nebraska were convinced by their pastors and temperance zealots to ban alcoholic beverages from the state. They put the Storz brewery out of business and Frederick Austerlitz out of work. He and his wife had long, late-night discussions about their future. They finally decided that Adele's talent [as a dancer] deserved better training than she could get in Omaha. Ann would take the two children to New York City; Frederick would stay in Omaha to earn money and support them.
Thomas, Astaire: The Man, The Dancer, page 16:
Through their career together, Fred and [his sister] Adele seemed content in their relationship, avoiding the competitiveness that has afflicted and often destroyed show-business teams... "It's funny," Fred said, "but there was a time--I was six and Adele was seven--when I used to think of her with contempt. She couldn't play ball, or chin herself, or whistle through her teeth. She couldn't even spit! I used to pray at night for God to turn her into a brother. Why, one day she even tied a pink ribbon in my hair... Then... when we had the first contest at dancing school...the judges gave us the first prize, with special mention for Adele. Then it began to dawn on my that she had her way of getting results and I had mine..."
From: Fred Astaire: Steps in Time: An Autobiography, page 5:
We [Fred and his sister and dancing partner Adele] made a habit of enjoying ourselves in private life. I don't mean that the work wasn't enjoyable, but we were fortunate enough to know how to live off stage.
My private life was No. 1 with me from the time of my marriage on. Before that, I suppose my career did come first. Everything changed when I married Phyllis in 1933.
Some time after Fred Astaire's sister Adele was widowed, she remarried. From: Thomas, Astaire: The Man, The Dancer, page 201:
...Adele had met an officer who was chief of intelligence in the Eighth Air Force, Kingman Douglass. The acquaintance was renewed in New York, where he worked as an investment banker. On April 28, 1947, Douglass, fifty-one, married [Adele] in the Presbyterian church of Warrentown, Virginia.
From: Thomas, Astaire: The Man, The Dancer, page 289:
If Adele [Fred Astaire's sister] never changed, the times did. During the 1960s and 1970s both America and England underwent social upheavals that changed forever the kind of world that Adele had known. Although she herself had always been totally frank, she railed at the new freedom. "All this sex stuff nowadays, it's so phony," she told a young friend. "I'd just love to see everyone get impotent. I think it would be great fun."