Hi, Since we have a van Ooijen in our family from Gelderland, I was interested. Try www.wiewaswie.nl
previously genlias.nl If you are not familiar with the site go the home page, Personen zoeken, under that go to Uitgebreid zoeken, then complete the listing. Ooijen, tussenvoegsel van, voornaam Pieternella then at the bottom Zoeken.
On the list that appears, you will see Gelderland (15) select that, then 2 pages will appear. At the bottom of the first page 1856 Pieternella appears, but more importantly with a relation to Cornelis Kiep. Perhaps one of the boys was named after him. Try the same search for Cornelis Kiep and see what comes up. Perhaps for some reason the boys kept their mother's name.
Good luck, Frans.