On Tab ReSelect PopToRoot - TabbedPage

Hi,
I'm facing a issue which seems simple but Im having a hard time trying to solve.

I use a TabPage on android that have a NavigationPage each:

        public class TabPage : CustomTabbedPage
            {
                public TabPage ()
                {
                    this.Children.Add(new NavigationPage( new firstPage() ) {Title = "First", Icon="first"});
                    this.Children.Add(new NavigationPage( new secondPage() ) {Title = "Second", Icon="second"});
                }
               )

I also use a CustomRenderer to show some icons on tabs.

What Im trying to achieve is, when you are navigating inside a tab and tap that tab again... it would PopToRoot.... all way down to the first page.

Should I override some specific method in customRenderer or there are a simpler way?

And another question... I dont have the iOS subscription right now but plan to get soon.
On iOS how these tabs behave? If reselect them it would go to rootPage?

Thanks