In the 1900 census did you also notice that he was born in Germany and stated he immigrated to the U.S. in 1892, 8 yrs NA (Naturalized Alien)? In 1910 census he and his brother Bernard are living in their married sister's household, Mary Koop, and all list came U.S. 1892. In 1930 he lists came U.S. 1892 became Naturalized 1898 and that he was born in Hanover (Germany). Check Immigration and Natualzation for his records of entry and becoming a citizen. Check Ellis Island website too.