Herman and his brother Edward married sisters Maria or Mary and Maryanne Niggeler, respectively. Therefore each family's children are double cousins with each other, which is significant genetically.
Daughter
Bertha Ann 'Burau' Williams
b 6 Sep 1880 Elizabeth, Otter Tail, MN
d 3 Apr 1972 Sacramento, CA

HERMAN BURAU
Herman Burau, deceased, was born on December 15, 1847, nl Germany, and after the death of his father, came with his mother to America and settled in Otter Tail county-, Minnesota, where he took up a homestead of one hundred and sixty acres, to which he later added forty acres more, making in all. two hundred acres at the time of his death. He was a blacksmith by trade, and conducted a shop at Elizabeth, being the first blacksmith in the town. He was a very progressive and prosperous man, and was an earnest member of the German Lutheran church. Mr. Burau put valuable improvements on his homestead, including a substantial house, which was built thirty-eight years ago.
()n October 2 1 . [868, Herman Burau was married to Mary Nigler, daughter of Rudolph and Elizabeth (Arn) Nigler. She was born on January 17. 1850, in Switzerland, and came with her parents to America in 1852.
To Herman and Mary (Nigler) Burau were born the following children: Rose. Mary, Charles, Helen. Emma, Bertha, Herman. Frank, John and Raymond, all of whom are now living. Rose Burau became the wife of Peter Wilmes and resides at Glen Cllin, North Dakota: Charles was married to Minnie Godfrey, and resides at Elizabeth: Helen became the wife of E. A. Forder and resides at Chisholm, Minnesota: Emma was married to Joseph Miller and lives at Elgin, North Dakota; Bertha is now Mrs. James Williams and lives at Grand Forks, North Dakota; Herman was married to Martha Becker and lives at Elizabeth, Minnesota ; John was united in marriage with Anna Johnson; Rose Burau, the eldest of this family of children, was the first white child born in Otter Tail county. Minnesota; the others were all born on the home place.
Frank Burau, the eighth child of Herman and Mary (Nigler) Burau, was born on April 26, 1885, at Elizabeth, Minnesota, and is unmarried. He lives on the old homestead and takes care of the place, which is located a quarter of a mile from Elizabeth. He is one of the progressive and up-to-date farmers of Otter Tail county, possessing a keen foresight along the lines of agriculture.
Rudolph and Elizabeth (Am) Nigler, parents of Mrs. Herman Burau, were both born in Switzerland, and came to America in 1852, locating first in Ohio and from there they moved to Minneapolis, Minnesota, where Mr. Nigler was engaged in business for several years, conducting a general store and a hotel, finally coming to Elizabeth in 1868, and taking up a homestead one and one-half miles west of that town. The farm consisted of one hundred and sixty acres, and was their home until their death. Politically, Mr. Nigler was a Democrat, and always took an active part in local politics. Both Mr. Nigler and his wife were members of the Lutheran church, and it was through him that the town of Elizabeth, Minnesota, was started, the place being named for his wife, Elizabeth (Arn) Nigler. They were the parents of the following children: Louise, Mary Ann. Rose, Minnie, Mary, Adolph and Edward; and reared Andrew, an adopted child.
Source: http://www.ebooksread.com/authors-eng/john-w-john-wintermute-mason/history-of-otter-tail-county-minnesota--its-people-industries-and-institutio-osa/page-87-history-of-otter-tail-county-minnesota--its-people-industries-and-institutio-osa.shtml