Necesito tener un script que pueda insertar / agregar nuevos nodos hijos xml a un nodo padre xml preexistente.

--New child nodes
DECLARE @XMLChildData XML
SET @XMLChildData = '
<Persons>
    <Person>
        <Firstname>Gary</Firstname>
        <Surname>Smith</Surname>
        <Telephone>0115547899</Telephone>
        <Address>
            <AddressLine>1 Church Lane</AddressLine>
            <AddressLine>Rosebank</AddressLine>
            <AddressLine>Houghton</AddressLine>
            <AddressLine>South Africa</AddressLine>
        </Address>
    </Person>
    <Person>
        <Firstname>Wayne</Firstname>
        <Surname>Farmey</Surname>
        <Telephone>0117453269</Telephone>
        <Address>
            <AddressLine>51 Oak Street</AddressLine>
            <AddressLine>Rivionia</AddressLine>
            <AddressLine>Sandton</AddressLine>
            <AddressLine>South Africa</AddressLine>
        </Address>
    </Person>
    <Person>
        <Firstname>Mark</Firstname>
        <Surname>Jones</Surname>
        <Telephone>0119854741</Telephone>
        <Address>
            <AddressLine>4 Arum Lane</AddressLine>
            <AddressLine>Glen Hazel</AddressLine>
            <AddressLine>Johannesburg</AddressLine>
            <AddressLine>South Africa</AddressLine>
        </Address>
    </Person>
</Persons>'

--Existing parent node
DECLARE @XMLParentData XML
SET @XMLParentData = '
<Persons>
    <Person>
        <Firstname>Sarah</Firstname>
        <Surname>Gray</Surname>
        <Telephone>0113265874</Telephone>
        <Address>
            <AddressLine>78 Emerl Aveune</AddressLine>
            <AddressLine>Fourways</AddressLine>
            <AddressLine>Sandton</AddressLine>
            <AddressLine>South Africa</AddressLine>
        </Address>
    </Person>
    <Person>
        <Firstname>Jenna</Firstname>
        <Surname>Reed</Surname>
        <Telephone>0114781102</Telephone>
        <Address>
            <AddressLine>6 Park Lane</AddressLine>
            <AddressLine>Parkhurst</AddressLine>
            <AddressLine>Rosebank</AddressLine>
            <AddressLine>South Africa</AddressLine>
        </Address>
    </Person>
    <Person>
        <Firstname>Mike</Firstname>
        <Surname>Wilke</Surname>
        <Telephone>0116532003</Telephone>
        <Address>
            <AddressLine>22 High Road</AddressLine>
            <AddressLine>Modderfontein</AddressLine>
            <AddressLine>Edenvale</AddressLine>
            <AddressLine>South Africa</AddressLine>
        </Address>
    </Person>
</Persons>'

Quiero que el resultado final sea:

<Persons>
    <Person>
        <Firstname>Sarah</Firstname>
        <Surname>Gray</Surname>
        <Telephone>0113265874</Telephone>
        <Address>
            <AddressLine>78 Emerl Aveune</AddressLine>
            <AddressLine>Fourways</AddressLine>
            <AddressLine>Sandton</AddressLine>
            <AddressLine>South Africa</AddressLine>
        </Address>
    </Person>
    <Person>
        <Firstname>Jenna</Firstname>
        <Surname>Reed</Surname>
        <Telephone>0114781102</Telephone>
        <Address>
            <AddressLine>6 Park Lane</AddressLine>
            <AddressLine>Parkhurst</AddressLine>
            <AddressLine>Rosebank</AddressLine>
            <AddressLine>South Africa</AddressLine>
        </Address>
    </Person>
    <Person>
        <Firstname>Mike</Firstname>
        <Surname>Wilke</Surname>
        <Telephone>0116532003</Telephone>
        <Address>
            <AddressLine>22 High Road</AddressLine>
            <AddressLine>Modderfontein</AddressLine>
            <AddressLine>Edenvale</AddressLine>
            <AddressLine>South Africa</AddressLine>
        </Address>
    </Person>
    <Person>
        <Firstname>Gary</Firstname>
        <Surname>Smith</Surname>
        <Telephone>0115547899</Telephone>
        <Address>
            <AddressLine>1 Church Lane</AddressLine>
            <AddressLine>Rosebank</AddressLine>
            <AddressLine>Houghton</AddressLine>
            <AddressLine>South Africa</AddressLine>
        </Address>
    </Person>
    <Person>
        <Firstname>Wayne</Firstname>
        <Surname>Farmey</Surname>
        <Telephone>0117453269</Telephone>
        <Address>
            <AddressLine>51 Oak Street</AddressLine>
            <AddressLine>Rivionia</AddressLine>
            <AddressLine>Sandton</AddressLine>
            <AddressLine>South Africa</AddressLine>
        </Address>
    </Person>
    <Person>
        <Firstname>Mark</Firstname>
        <Surname>Jones</Surname>
        <Telephone>0119854741</Telephone>
        <Address>
            <AddressLine>4 Arum Lane</AddressLine>
            <AddressLine>Glen Hazel</AddressLine>
            <AddressLine>Johannesburg</AddressLine>
            <AddressLine>South Africa</AddressLine>
        </Address>
    </Person>
</Persons>

Sé que necesito usar .modify (), sin embargo, no estoy seguro de cómo recorrer los nodos secundarios e insertar / agregar cada niño"<person>" nodo en el padre"<persons>" nodo.

Creo que debería ser algo similar a lo siguiente

SET @XMLParentData.modify('
    insert     
        (
            sql:variable("@XMLChildData")
        )
    after
        (/Person[1]/Person[1])
')

SELECT @XMLData