The 37-year-old posted the video to Instagram, showing Harvey, 12, trying to make his baby sister laugh.
Mum-of-five Katie tells Harvey to tickle Bunny, 10 months, while she's having her bottle.
And it's not long before the little girl is laughing along with her big brother!
"so cute Harvey with Bunny," Katie gushed.
Katie also shared a video of her son Jett Riviera, 20 months, running in from the rain with his dad, 27-year-old Kieran Hayler.
She tells him to run in from the downpour before he turns around, clearly fascinated by the rain.
The former glamour model's followers were quick to praise her, commenting about her parenting skills on both of the videos.
One wrote: "That's really sweet. Exactly how kids should be. You are very blessed to have 5 perfect kids [sic]."
Another said: "Lovely to see a celebrity's child enjoying a normal childhood [sic]."