The name William Rea appears in the South Fork Fishing and Hunting Club, Guest Register, 1886. He is most likely a relative of Samuel Rea, although more research is needed to determine exactly what his relation was. Since both William and Samuel's name appears on the Guest Register, it is unlikely that Samuel's name was mistakenly written as William.
Thanks to researcher John Leach, the following information was discovered:
There are two possibilities for William Rea. Samuel Rea had a brother named William, who was 66 years old in 1886. This William also had a son, William Holdship Rea, who was 30 years old in 1886.
The older William Rea worked for the Pennsylvania Canal Co. and then co-founded Robinson, Rea & Co., which made equipment for steel mills.
The son also worked in the company. The other thing that's important about the son is that his wife was Mary (Childs) Rea, whose cousin Adelaide was the wife of Henry Clay Frick.
William Rea generally was called that, while William Holdship Rea generally was called William H. Rea.