The local newspaper is online and it mentioned that on 12-sep-1939 a daughter is born ( without mentioning her name ) from J. Zonneveldt-Sival. Then I found on 30-dec-1936 in Haarlem a M.C. Zonneveldt married J. Sival. The only M.C. I could find on is a Matthijs Cornelis born 07-Nov-1900 Velsen , son of Matthijs Zonneveldt and Clasina Hoogeduin. Have a look yourself on http://haarlem.digitalestamboom.nl/
I think he was married before with Albertine Neumann on 11-sep-1924 Velsen and divorced 10-Dec-1936. I couldn't find info on J. Sival but on this moment I guess she is a daughter of Jacobus Sival and Jacoba Vermaas.