Looks very promising. You probably already thought this through but make sure you don't allow:
-Objects to be their own parents/children. (Ex: You can't be your own mother or daughter.)
-Children to have multiple parents (this seems so sad
)
-The child of the parent to be the parent's parent. (Ex: Your son can't also be your father.)
-Other "recursive" parenting
You could always allow some of these things above, (like multiple parents) but just make it clear for the user.