Yes, it can but you have to use the $controller
service to instantiate the controller instead:-
var app = angular.module('angularjs-starter', []);
app.controller('ParentCtrl', function($scope) {
// I'm the sibling, but want to act as parent
});
app.controller('ChildCtrl', function($scope, $controller) {
$controller('ParentCtrl', {$scope: $scope}); //This works
});