When Johannes Friedrich Wilhelm Grabau was born on 4 January 1878, in Cedarburg, Ozaukee, Wisconsin, United States, his father, Rev Heinrich Wilhelm Grabau, was 41 and his mother, Maria Sophia Wilhelmine Von Rohr, was 33. He married Minnie Fannie Mason on 27 February 1900, in Buffalo, Erie, New York, United States. They were the parents of at least 1 son and 4 daughters. He lived in Buffalo, Erie, New York, United States for about 40 years. He died on 20 June 1948, in Williamsville, Amherst, Erie, New York, United States, at the age of 70, and was buried in Buffalo, Erie, New York, United States.