i found the solution....you have to add this piece of code in a partial class:
[AssociationEndBehavior("AccountingPositions", Owned = true)]
[AssociationEndBehavior("AccountingInterOUs", Owned = true)]
[AssociationEndBehavior("AccountingDetail", Owned = true)]
public partial class AccountingHeader { }
when deleting the parent object you will get an error if you don't use that code create a partial class and above it write
[AssociationEndBehavior("Child1", Owned = true)]
for all child even the one that you don't want to update...regrds