He is married to Johanna Penninx.
They got married on June 24, 1729 at Son, Noord-Brabant, Nederland, he was 27 years old.Source 2
Child(ren):
FamilySearch: Family Tree
Johannis Mercks
Birth 2 February 1702 • Son en Breugel, Noord-Brabant, Nederland
Spouse Johanna Penninx
Children Catharina Christina Jansse Merx
Lead confidence: 5
https://www.familysearch.org/tree/person/GW4W-V2G
"Nederland, Indexen van de Archieven, Primaire Archiefstukken (BS en DTB), 1600-2000," database, FamilySearch (https://familysearch.org/ark:/61903/1:1:QLD2-R2T4 : 23 August 2017), Joannes Cornelius Merx in entry for Christina Merx, Baptism 23 Feb 1743, Son, Noord-Brabant, Nederland; from database, openarchives (https://www.openarch.nl : 2016); citing Doop-, trouw- en begraafboek Son, archive 10225, inventory number 52.1, folio; Doop-, trouw- en begraafboek Son; Regionaal Historisch Centrum Eindhoven.
https://familysearch.org/ark:/61903/4:1:GW4W-V2G