Paul Junghans' older brother Otto married Hulda Hahmann in Mequon, Wisconsin on July 1, 1883.
According to the records I obtained in Mequon, an index card had been completed naming Otto's parents, which helped me decipher the handwriting from Paul's marriage document in Milwaukee. I can only assume Otto was guessing as to the year of his parent's marriage, because Emil was born in 1855 and Carl in 1858 and Otto in 1861.
Or the 1860 number was just a clerical error.
The other error I noted was Otto's birth year of 1862, which conflicts with the birth of his younger brother Paul, who was born December 20, 1862. Otto's birth date is September 2, 1861.
If you accumulate enough documents, you can generally weed out the mistakes or make an educated guess with enough information. Even tombstones can be inaccurate.