Add and Remove ChildViewController

gistfile1.m

// add child view
    UIViewController* controller = [self.storyboard instantiateViewControllerWithIdentifier:@"test"];
    [self addChildViewController:controller];
    controller.view.frame = CGRectMake(0, 44, 320, 320);
    [self.view addSubview:controller.view];
    [controller didMoveToParentViewController:self];

// remove child view
    UIViewController *vc = [self.childViewControllers lastObject];
    [vc.view removeFromSuperview];
    [vc removeFromParentViewController];

You should call [vc willMoveToParentViewController:nil]; before removeFromSuperview;

UIViewController *vc = [self.childViewControllers lastObject];
[vc willMoveToParentViewController:nil];
[vc.view removeFromSuperview];
[vc removeFromParentViewController];

https://gist.github.com/tomohisa/2897676#gistcomment-1209661

官方文档已经讲得很清楚...

Implementing a Custom Container View Controller
https://developer.apple.com/library/ios/featuredarticles/ViewControllerPGforiPhoneOS/CreatingCustomContainerViewControllers/CreatingCustomContainerViewControllers.html