I found in 1850 Census in Vinton Co., OH Benjamin Yarger and wife Hannah, next door is James Yarger and Panina with Sylvester Lewis age 2. This tells me that Wm. Sylvester was Peninah's child. Born two years before she married James Yarger. I don't know if she was married before or if Sylvester was born out of wedlock.
I have seen trees with Peninah Lewis daughter of Samuel and Margaret D. Lewis so if her maiden name was Lewis then probably Sylvester was illegitimate. Also her age in 1850 was 23 but in 1860 it was 25. I think the 1860 age is probably wrong. It does make for more possible questions though.