If you are interested in descendants of Jacob Rees (incorrectly spelt Reez in the church indices) and Elizabeth Shultz you can contact me directly at firstname.lastname@example.org
I recently travelled to Lancaster County and spent a day at the county Historical Society and found documents confirming Jacob was my ancestor who went to Pelham Township, Upper Canada circa 1788.
I also have a lead into Jacob Rees' father. I believe he was named Thomas Rees. As you can see from the marriage records Jacob married Elizabeth Shultz the daughter of Andrew Shultz of Lampeter Twp. While at the historical society I looked at a book of original warrants for land in Lancaster County. There were two entries for Rees: Morgan Rees of Martic Twp. and Thomas Rees of Lampeter Twp. Based on geography and dates I would say that Jacob Rees was a brother to George and John and that Thomas was their father.