There might be some additional information in the other one. Check the church records whether the people you're looking for were members of the church. If they came from another town, they had to show an attestation from the former community. Read in magazines how other people attacked their problems. Maybe the same trick will do it for you.
Judicial records can also give a lot of information on relationships between people.
Last wills can give you an insight of family relations. For the Achterhoek area in the mid 1700's, try the ' Liberale Gifte ' of 1748. This is like a census record and lists all the families at that time. Ask questions in magazines or newsgroups such as soc.genealogy.benelux , and share your ahnentafel with many people.