Create Table Hierarchy??

Hi, with the three tables below, I want to add relationships so that each Grandparent can spawn many parents and each Parent can spawn many children.

I keep getting an error when I try to connect them. Could I get some help creating that hierarchy please?

Thanks in advance!

Here are the tables:

CREATE TABLE [dbo].[GrandParent] (
[GPID] [int] IDENTITY (1, 1) NOT NULL ,
[GPName] [varchar] (50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL
) ON [PRIMARY]
GO

CREATE TABLE [dbo].[Parent] (
[PID] [int] NOT NULL ,
[GPID] [int] NOT NULL ,
[PName] [varchar] (50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL
) ON [PRIMARY]
GO


CREATE TABLE [dbo].[Child] (
[CID] [int] NOT NULL ,
[PID] [int] NOT NULL ,
[ChName] [varchar] (50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL
) ON [PRIMARY]
GO


--PhB