Wpf binding nested enitities

hellow all, I have to bind an entity to wpf controls, also to bind it's nested object properties. it works fin until I try to create new object . then the nested object is not binded . I am using mvvm . the antities are detachad and came from wcf service.   this is part of my xaml: 

<Label Grid.Column="0" Grid.Row="0" Content="כתובת מגורים" />

<TextBox Grid.Column="1" Grid.Row="0" Text="{Binding Path=Family.Address, Mode=TwoWay, UpdateSourceTrigger=LostFocus, NotifyOnValidationError=True, ValidatesOnDataErrors=True, ValidatesOnExceptions=True}" />

<Button Grid.Row="1" Padding="10" Command="{Binding SaveCommand}" Content="שמור" />

  this is part of the VM:

void SaveExecute(object param)

if (!Globals.IsLocal)

ServiceReference1.ChildServiceClient proxy=new ServiceReference1.ChildServiceClient();

proxy.SaveChild(Child);

else

WcfServiceData.ChildService s=new WcfServiceData.ChildService();

s.SaveChild(Child);

//if (!context.Childs.Any(x=>x.IdentityNum==Child.IdentityNum ))

// context.Childs.AddObject(Child);

//context.SaveChanges();

void FindExecute(object param)

SearchState = Visibility.Visible;

//SearchCommand

void NewExecute(object param)

Child =new Child();

Child.Family=new Family();

Child.FamilyId= 0;

Child.Family.FamilyName="type name";

when the entity is old- all works and the changes saved successfully. but when the entity is new- even the text "type name" is not displayed.

m.sh