KWPN Hengstenboek Supplement Fokfamilies - Foundation Mare Families Supplement pages for the Hengstenboek-Active Stallions volumes or the Hengstenboek System (see category: Dutch Warmbloods) to keep your volumes up-to-date. This supplement gives breeding family number, foundation mare of that family, the approved stallions, notable sport horses and prestatiemerries within the family, each with registration number and sire x dam's sire.