The setup (simplified)

public interface IHierarchical : IEntity
{
    [Field(Nullable = false)]
    Hierarchy Hierarchy { get; set; }
}
public interface IHierarchical<T> : IHierarchical where T : IHierarchical<T>
{
    [Field]
    T Parent { get; set; }
}

public class TestPerson : Entity, IHierarchical<TestPerson>
{
    public Hierarchy Hierarchy { get; set; }

    public TestPerson Parent { get; set; }
}

For this, I'll get 2 indexes for Parent field, which look like theese:

CREATE NONCLUSTERED INDEX [TestPerson_IHierarchical(TestPerson)_FK_Parent] ON [dbo].[TestPerson] 
(
    [Parent_Id] ASC
)
CREATE NONCLUSTERED INDEX [TestPerson_FK_Parent] ON [dbo].[TestPerson] 
(
    [Parent_Id] ASC
)

Obviously one of these indexes is redundant