Binding SelectedItem to ItemsSource between two datagrids

<UserControl x:Class="NestedDataGrid.MainPage"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             mc:Ignorable="d"
             xmlns:data="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Data"
             xmlns:telerik="clr-namespace:Telerik.Windows.Controls;assembly=Telerik.Windows.Controls.GridView"
             xmlns:this="clr-namespace:NestedDataGrid"
             xmlns:commands="clr-namespace:Microsoft.Practices.Composite.Presentation.Commands;assembly=Microsoft.Practices.Composite.Presentation"
             >
    
        
        
		
        <data:DataGrid x:Name="dgTeams"
                       SelectedItem="{Binding SelectedTeam}"
                       ItemsSource="{Binding Teams}" 
                       this:DataGridRowSelected.Command="{Binding GridViewRowSelectedCommand}"
                       />
        

        
        

		
        <Button Content="Delete Current"
                commands:Click.Command="{Binding DeleteCurrentTeamCommand}"
                commands:Click.CommandParameter="{Binding SelectedTeam}"
                />

    

public partial class MainPage : UserControl
{

    ViewModel viewModel = new ViewModel();

    public MainPage()
    {
        InitializeComponent();
        this.LayoutRoot.DataContext = viewModel;
    }

}

public class ViewModel: ObjectBase
{
    ObservableCollection _rainbowPeeps;
    ObservableCollection _theSimpsons;
    ObservableCollection _familyGuyKids;


    public ViewModel()
    {
        /// setting up some dummy data
        _rainbowPeeps = new ObservableCollection()
        {
            new Person(){ PersonId=1, Name="George"},
            new Person(){ PersonId=2, Name="Zippy"},
            new Person(){ PersonId=3, Name="Bungle"},
        };

        _theSimpsons = new ObservableCollection()
        {
            new Person(){ PersonId=4, Name="Moe"},
            new Person(){ PersonId=5, Name="Barney"},
            new Person(){ PersonId=6, Name="Selma"},
        };

        _familyGuyKids = new ObservableCollection()
        {
            new Person(){ PersonId=7, Name="Stewie"},
            new Person(){ PersonId=8, Name="Meg"},
            new Person(){ PersonId=9, Name="Chris"},
        };


        Teams = new ObservableCollection()
        {
            new Team(){ TeamId=1, TeamDesc="Rainbow", People=_rainbowPeeps},
            new Team(){ TeamId=2, TeamDesc="Simpsons", People=_theSimpsons},
            new Team(){ TeamId=3, TeamDesc="Family Guys", People=_familyGuyKids },
        };

        /// COMMAND IMPLEMENTATIONS. The DataGridRowSelected parameter
        /// is the datacontext of the selected row.
        GridViewRowSelectedCommand = new DelegateCommand(
            delegate(Team team) { SelectedTeam = team; }
            );

        DeleteCurrentTeamCommand = new DelegateCommand(
                delegate(Team team)
                {
                    Teams.Remove(team);
                    if (Teams.Count > 0)
                        SelectedTeam = Teams[0];
                    else
                        SelectedTeam = null;
                }
            );
    }

    private ObservableCollection _teams;
    public ObservableCollection Teams
    {
        get { return _teams; }
        set
        {
            SetValue(ref _teams, value, "Teams");
        }
    }

    private Team _selectedTeam;
    public Team SelectedTeam
    {
        get { return _selectedTeam; }
        set
        {
            SetValue(ref _selectedTeam, value, "SelectedTeam");
        }
    }

    /// 

    /// Command to handle the selection of a row.
    /// 

    private DelegateCommand _gridViewRowSelectedCommand;
    public DelegateCommand GridViewRowSelectedCommand
    {
        get { return _gridViewRowSelectedCommand; }
        set
        {
            SetValue(ref _gridViewRowSelectedCommand, value, "GridViewRowSelectedCommand");
        }
    }

    /// 

    /// Used to simulate the deletion of a parent team
    /// 

    private DelegateCommand _deleteCurrentTeamCommand;
    public DelegateCommand DeleteCurrentTeamCommand
    {
        get { return _deleteCurrentTeamCommand; }
        set
        {
            SetValue(ref _deleteCurrentTeamCommand, value, "DeleteCurrentTeamCommand");
        }
    }

}

public abstract class ObjectBase : Object, INotifyPropertyChanged
{
    public ObjectBase()
    { }

    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void _OnPropertyChanged(string propertyName)
    {
        PropertyChangedEventHandler pceh = PropertyChanged;
        if (pceh != null)
        {
            pceh(this, new PropertyChangedEventArgs(propertyName));
        }
    }

    protected virtual bool SetValue(ref T target, T value, string propertyName)
    {
        if (Object.Equals(target, value))
        {
            return false;
        }

        target = value;
        _OnPropertyChanged(propertyName);

        return true;
    }

}


public class Person: ObjectBase
{
    private int  _personId;
    public int PersonId
    {
        get { return _personId; }
        set
        {
            SetValue(ref _personId, value, "PersonId");
        }
    }

    private string _name;
    public string Name
    {
        get { return _name; }
        set
        {
            SetValue(ref _name, value, "Name");
        }
    }

}

public class Team : ObjectBase
{

    private int _teamId;
    public int TeamId
    {
        get { return _teamId; }
        set
        {
            SetValue(ref _teamId, value, "TeamId");
        }
    }

    private string _teamDesc;
    public string TeamDesc
    {
        get { return _teamDesc; }
        set
        {
            SetValue(ref _teamDesc, value, "TeamDesc");
        }
    }


    private ObservableCollection _people;
    public ObservableCollection People
    {
        get { return _people; }
        set
        {
            SetValue(ref _people, value, "People");
        }
    }

    public override string ToString()
    {
        return _teamId.ToString() + " " + _teamDesc;
    }

}