I know I am going to get into trouble for this answer, Joseph Ditto is traditionaly the name of Francis Lewis' father. I cannot find records of Joseph in Pa. The proof is all antecdotal. Thre is an administration for Francis' mother, Barbara Deeto/Ditto, in York Co. Pa. It names, John, Jacob, Francis, Joseph, Anthony, Catharine and Mary in that order. It also states John was the oldest. Judging by the administor of her estate Casper White/Weise she lived either in Berwick Twp (now Adams Co) or Paradise Twp. York Co. Pa. It gives no indication who his twin might be. If you would like a copy of this document, contact me at firstname.lastname@example.org.