Jordan's tribute, which includes drawings, has proven a hit on social media as Springbok great Van der Westhuizen's death last week from motor neurone disease continues to make headlines.
Former Liverpool goalkeeper Sander Westerveld, who now plays in South Africa, posted it on Twitter, clearly touched by the 13-year-old's love for his father and the famous football club.
Jordan wrote: "Thank you for everything but most of all for 'being the best you can be!' You are the best rugby player in the world. I want to be the best sportsman like you, because you said I must work hard.
"I will always love you to the moon [and] back.
"Daddy please tell God that Liverpool must win. You will never walk alone! I love you so much."
Van der Westhuizen, who played 89 times for the Springboks, was honoured at a public memorial service in Pretoria last Saturday (NZ time).
Westerveld felt there may have been some divine intervention in Liverpool's latest win, a 2-0 effort against Spurs at Anfield last weekend.
Photo: Twitter (Jonah Lomu with Joost van der Westhuizen and his children Jordan and Kylie. Jordran (left) has penned a tribute to his father).