The tour of BMD records of my great-grandparents ends with the birth certificate of Johanna Petronella Moerman, number 15 in my ahnentafel:
On 12 May 1875 appeared for the registrar: Cornelia Visser, 43, midwife. She declared that on the 11th of same month, at 6 am, in a house on the Zonneblomsteeg street, a female child was born from Johanna Petronella Brandenburg, to whom she gave the names Johanna Petronella.
A note in the margin, added on 26 August 1876, states that the child was acknowledged and legitimated by Cornelis Jacobus Moerman and the mother at their wedding on 23 August 1876.
So my great-grandmother was born illegitimate, as Johanna Petronella Brandenburg. Over a year later her mother married and she was legitimated, and her name changed to Johanna Petronella Moerman. Was she really a daughter of C.J. Moerman? Legally, yes, but biologically? I don't know, and probably never will.