Thanks Sandra. Since I first posted I have found some additional information. I may be getting close to figuring out where Peter's father Peter lived and/or died so I will have to try to check out the wills.
Some trees say father Peter died in Allegheny Co, Pa. I found "son" Peter listed in a book on Fayette Co, Pa. Trees state he was born in Cumberland Co and Lancaster Co in Pa as well as in Virginia. I did research on the counties and all of these entries make sense - Fayette Co was originally part of Lancaster, then Cumberland, then Fayette. At one point, Fayette was claimed by both Pa and Virginia in a border dispute which lasted several years.
At least now I have some leads to follow. I'll try to find a site which lists wills in Allegheny and Fayette Counties in Pa.