There is also Edward WEBB who lived in Allegheny, Butler, Washington Counties in Pennsylvania. He likely is the one who died in November 1869 in Lawrence County, PA.
He is the son of James, who is the son of John. See the Butler County, Pennsylvania History.
John was a British Officer. He moved his family from England to Philadelphia. He was killed in Quebec in 1759. His widow and two children moved to Franklin County, Pennsylvania, where she had friends.
She was killed by the Indians. James was captured. He was 11 years old. He escaped when he was 18 years old. He returned to Franklin County, where he married a woman by the maiden name of BROWN.
After the Revolutionary War, James moved to Allegheny County; where he lived out the remainder of his life. The history lists three sons, one being Edward. No Isaac.
SO, could Isaac be from a sibling of James?