from the Warrington MM records; Jesse Cook, son of Peter Cook and Sarah his wife of Warrington, married Mary Wierman, dau of Henary Wierman and Priscilla, his wife at HuntingtonSept 24, 1767.
Peter cook d 22-4-1779, aged 79 Sarah cook d 7-6-1783, agec about 77....lists all their children including Jesse b 15-9-1744 d 18-8-1816.
There is no marriage record for Sydney and Isaac.
The only listing for an Isaac Cook is as the son of Jacob and Mary Cook, b 28-6-1772, with siblings Abraham, Mary, and Lydia.
Pennsylvania Wills, 1682-1834 January 17, 1777April 7, 1784 Cook, Peter.Executors:Samuel and Jesse Cook.Warrington Township.Wife:Sarah Cook.Children:Jesse, Joseph, Samuel, Hannah, Ann, Sarah, and Peter. (I found a will for a David Evans, in York Co, but no Sydney...looks to be a different David, and it is the only one I found....nor did I find the name Sydney Evans or Cook in any area wills, in any way. I don't have a complete set of Warrington meeting records so you might want to do a LDS place check for York Co, PA and see if they might have all the Warrington records on film.