I need to get child publications of a publication. I am using the following approach: get "where used" for the publication. Until now my code looks like this:

    var id = publicationParent5TcmId;
    var filter = new Tridion.ContentManager.ListFilter({columns: const.ColumnFilter.DEFAULT |$const.ColumnFilter.ALLOWED_ACTIONS |  $const.ColumnFilter.VERSIONS,    conditions:{InclLocalCopies: true}});

        var brothersPublications;
        var onSuccess = function () {
            if (brothersPublications) {
                $log.debug("WhereUsed.GetListUsingItems success: found " + brothersPublications.length + " brothers publications");
            }
            else {
                $log.debug("WhereUsed.GetListUsingItems success");
            }
        };

        var onFailed = function () {
            $log.debug("WhereUsed.GetListUsingItems failed");
        };
        
        brothersPublications = tridion.Web.UI.ContentManager.WhereUsed.GetListUsingItems(id, filter.conditions, filter.columns, onSuccess, onFailed);
        

It enters in onSuccess function, but brothersPublications is undefined.