FOR XML Query With More Than 2 Levels Of Data

I'm having trouble getting a FOR XML query to get the relationships correct when there are 3 levels of data.

In this example, I have 3 tables, GG_Grandpas, DD_Dads, KK_Kids. As you would expect, the Dads table is a child of the Grandpas table, and the Kids table is a child of the Dads table.

I'm using the Bush family in this example, these are the relationships:
- George SR
--- George JR
------ Jenna
------ Barbara
--- Jeb
------ Jeb JR
------ Noelle

These statements will create and populate the tables for the example with the above relationships:

SET NOCOUNT ON
DROP TABLE KK_Kids, DD_Dads, GG_Grandpas
CREATE TABLE GG_Grandpas ( GG_Grandpa_Key varchar(20) NOT NULL, GG_GrandpaName varchar(20))
CREATE TABLE DD_Dads ( DD_Dad_Key varchar(20) NOT NULL, DD_Grandpa_Key varchar(20) NOT NULL, DD_DadName varchar(20))
CREATE TABLE KK_Kids ( KK_Kid_Key varchar(20) NOT NULL, KK_Dad_Key varchar(20) NOT NULL, KK_KidName varchar(20))

ALTER TABLE GG_Grandpas ADD CONSTRAINT PK_GG PRIMARY KEY (GG_Grandpa_Key)
ALTER TABLE DD_Dads ADD CONSTRAINT PK_DD PRIMARY KEY (DD_Dad_Key)
ALTER TABLE KK_Kids ADD CONSTRAINT PK_KK PRIMARY KEY (KK_Kid_Key)
ALTER TABLE DD_Dads ADD CONSTRAINT FK_DD FOREIGN KEY (DD_Grandpa_Key) REFERENCES GG_Grandpas (GG_Grandpa_Key)
ALTER TABLE KK_Kids ADD CONSTRAINT FK_KK FOREIGN KEY (KK_Dad_Key) REFERENCES DD_Dads (DD_Dad_Key)

INSERT INTO GG_Grandpas VALUES ('GG_GEORGESR_KEY', 'GEORGE SR')
INSERT INTO DD_Dads VALUES ('DD_GEORGEJR_KEY', 'GG_GEORGESR_KEY', 'GEORGE JR')
INSERT INTO DD_Dads VALUES ('DD_JEB_KEY', 'GG_GEORGESR_KEY', 'JEB')
INSERT INTO KK_Kids VALUES ( 'KK_Jenna_Key', 'DD_GEORGEJR_KEY', 'Jenna' )
INSERT INTO KK_Kids VALUES ( 'KK_Barbara_Key', 'DD_GEORGEJR_KEY', 'Barbara' )
INSERT INTO KK_Kids VALUES ( 'KK_Noelle_Key', 'DD_JEB_KEY', 'Noelle' )
INSERT INTO KK_Kids VALUES ( 'KK_JebJR_Key', 'DD_JEB_KEY', 'Jeb Junior' )


So the question is, how do I get it to maintain the proper relationships between the records when I do an FOR XML query? Here is the query I am trying to get to work. Right now it puts all the Kids under a single Dad, rather than having them under their correct dads.
I am getting this, which is not what I want:

- George SR
--- George JR
--- Jeb
------ Jenna
------ Barbara
------ Jeb JR
------ Noelle


SELECT 1 as Tag,
NULL as Parent,
GG_GrandpaName as [GG_Grandpas!1!GG_GrandpaName],
GG_Grandpa_Key as [GG_Grandpas!1!GG_Grandpa_Key!id],
NULL as [DD_Dads!2!DD_DadName],
NULL as [DD_Dads!2!DD_Dad_Key!id],
NULL as [DD_Dads!2!DD_Grandpa_Key!idref],
NULL as [KK_Kids!3!KK_KidName],
NULL as [KK_Kids!3!KK_Dad_Key!idref]
FROM GG_Grandpas
UNION ALL
SELECT 2 ,
1 ,
NULL ,
GG_Grandpa_Key ,
DD_DadName ,
DD_Dad_Key ,
DD_Grandpa_Key ,
NULL ,
NULL
FROM GG_Grandpas, DD_Dads
WHERE GG_Grandpa_Key = DD_Grandpa_Key
UNION ALL
SELECT 3 ,
2 ,
NULL ,
GG_Grandpa_Key ,
NULL ,
DD_Dad_Key ,
NULL ,
KK_KidName ,
KK_Dad_Key
FROM GG_Grandpas, DD_Dads , KK_Kids
WHERE GG_Grandpa_Key = DD_Grandpa_Key
AND DD_Dad_Key = KK_Dad_Key

FOR XML EXPLICIT


I've tried it all different ways, but no luck so far.
Any ideas?