I did a quick search and found the following:
Gerrit's wife name is also been spelt as Hiltje Klazes in the death record of Gerrit's daughter, Hiltje Gerrits Walker, who died in Ferwerderadeel, Friesland, Netherlands on 9 SEP 1840 at age 68. Hiltje Gerrits Walker's husband has his name spelt as Menze Douwes Buursma.
I found a death certificate for a Hiltje Klase for 27 december 1816 in Ameland ( a West Frisian island), Friesland, Netherlands. Her age at death is listed as 72, which would make her birth date about 1744. No spouse or parents are listed in the record result.
Will keep looking though