The mother-of-five uploaded the touching family moment to her YouGossip account overnight, adding the caption: "My Harvey reading a book to Jett. Sooo cute."
Harvey is twelve years old and he's Katie's eldest child. His dad is former footballer Dwight Yorke. Jett, meanwhile, is just one year old. His dad is Katie's husband Kieran Hayler.
Alongside the adorable sibling moment, model Katie also shared another picture of Harvey, saying: "So proud of my baby boy. I love him more than words can describe."
Katie posted the picture to encourage fans to donate to Jeans for Genes, saying they can "make a difference" to children like Harvey. The organisation raises money for Genetic Disorders UK and works with children born with genetic disorders and their families.
Little Harvey has Septo-Optim Dysplasia and autism, as well as mobility and behavioural problems. Since his birth, Katie has devoted much time to raising awareness for his condition and supporting charities.
Katie has three other children: Princess and Junior, from her marriage to Peter Andre, and newborn baby daughter Bunny, her second child with husband Kieran.
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