There is a Sylvester Cupp in my family. He was born approx. 1857 in the Fairfield County OH area. Parents were James William Cupp and Charlotte Milligan, and they had three sons: Lafayette, Sylvester, and Lyman. Charlotte died in 1864, and James married Rachel Noice in 1866. It seems that the 3 boys were raised by others, possibly Charlotte's family, as the boys aren't in the census records with James and Rachel.
I don't have any additional information on Sylvester, but hope to fill in the blanks at some point.