Barbara, happy to see your message here. We're also researching the Abraham > Gershom Vanderhule family. We were wondering if your sister's book (your grandfather's) lists all of Abraham's children.
There is probably information we could share. I have Abraham's father as Henry, baptized in the Dutch Church, New York (city) in 1728. Then we have a land record of his in Monmouth County, NJ (there are probably others, if we could find them), and we think he died not long after 1804.
How far back does your sister's book go?