Please scan his diary and other documents as birthcertificates, marriage etc. I will try to translate.
There is a familybook HOLTROP 1634-1900 available. http://wiki-de.genealogy.net/Holtrop,_OFB
Our Group owns it and I will look for your ancestors in August.
Holtrop is situated in East Frisia, near Aurich
Please look for the OGSAhttp://www.ogsa.us/
The Ostfrisian Ortssippenbücher are also inhttp://www.tcghs.org/OSB.htm
They are helpful