private TreeModel generateTreeModel() {
        root = new DefaultMutableTreeNode("Personen");
        for (Persoon p : admin.personen) {
            DefaultMutableTreeNode persoon = new DefaultMutableTreeNode(p);
            if (!(p.getOuders() == null)) {
                addChildren(persoon, p);
            }
            root.add(persoon);
        }
        return new DefaultTreeModel(root);
    }