two tab bar controllers

You need a view and two UITabBar components as subviews. Of course, the parent view controller must be set as delegate to both of them in order to handle the user interactoins.

I think this will work if you are not using Storyboard. (Not sure how to do it if you are using Storyboard.)

in AppDelegate define global variables

UITabBarController *tabBarController1;

UITabBarController *tabBarController2;

then in didFinishLaunchingWithOptions;

    tabBarController1=[[UITabBarController alloc] init];
    tabBarController1.delegate=self;
    tabBarController2=[[UITabBarController alloc] init];
    tabBarController2.delegate=self;

then somewhere and certainly execute before leaving didFinishLaunchingWithOptions:

window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
if(groupAIsBeingDisplayed){
    window.rootViewController = tabBarController1;
}else{
     window.rootViewController = tabBarController2;
}

[window makeKeyAndVisible];

I draw 2 tabbarviewcontrols in the stroyboard,

how to connect tabBarController1 or tabBarController2 into the tabbarcontrols in the storyboard?