List<MyObject> _localCollection = new List<MyObject>();
List<MyObject> LocalCollection
{
   get { return _localCollection; }
   set
   {
     _localCollection = value;
     OnPropertyChanged("LocalCollection");
   }
}

<GridView Name="grdItems">
  <GridViewColumn>
    <GridViewColumn.Header>
      <CheckBox/>
    </GridViewColumn.Header>
    <!--Column Template-->
    <GridViewColumn.CellTemplate>
      <DataTemplate>
         <StackPanel Orientation="Horizontal">
           <CheckBox Tag="{Binding ObjID}"
                     IsChecked="{Binding ToRemove, Mode=OneWay}"
                     Checked="SelectRelative" />
         </StackPanel>
      </DataTemplate>
    </GridViewColumn.CellTemplate>
  </GridViewColumn>

private void SelectRelative(object sender, RoutedEventArgs e)
 {
    Dispatcher.BeginInvoke((Action)(() =>
    {
      //Get the Object Id we need
      int selectedId = Convert.ToInt32(((CheckBox)sender).Tag);
      //Get all objects that share this ID
      List<MyObjects> objLst = new List<MyObjects>(((IEnumerable<MyObjects>)grdItems.ItemsSource));

      //Clear the local collection property of our items used in the items source
      LocalCollection.Clear();
      //Remove the items source since we are updating it
      grdItems.ItemsSource = null;
      //Go through each item in the list and if the object id's match select them to remove
      foreach(var item in objLst)
      {
        if(item.ObjId == selectedId)
          item.ToRemove = true;
        //Add the object to our property
        LocalCollection.Add(item);
      }
      //Re-establish the item source with our new collection
      grdItems.ItemsSource = LocalCollection;
    }));
 }