I'm sorry I can't give you a more satisfactory answer, but my best source on the Readings says that Governor John (not George) had a son, George, who fought in the Revolution and married Rebecca Mullen. They had only two daughters, of whom one, Elizabeth, died rather young and the other of whom, Amelia, married Albert Joost Zabriskie. George and Rebecca did have a son, George, who married Nancy McCune, and they had a daughter Rebecca, but she married a William Holliday. If you could give me some dates for your Rebecca, I might be able to fish around a little more for Mr. Margerum. It's a great name - I'd like to be related!