Joseph Seiler Jr

The only information available is the 1860 census that list Joseph Seiler as 6/12 years old born in Chicago Illinois.  This might just be Benjamin Seiler.

The 1860 census was Enumerated on July 9, 1860.  6 months prior to this date would be February 1860.  So Joseph/Benjamin Seiler would have been born in December 1859 or January 1860.