'That's a bad word. Mommy's gonna get really mad at you,' the 29-year-old had said, as he instructed King Cairo not to say it.
The video begins with Cairo playfully asking: 'Can I have it?' as a quick shot of his adorable face turns to a view of underneath the bed, as he seemingly takes hold of the phone.
Cairo then excitedly announces he's going to 'see what's under the bed,' and turns the camera to do just that. Apparently the little boy then saw something he didn't like, as he could be heard shouting: 'Aw, st!'
He then repeated it twice more, before shining the camera on Rob's face, bundled up in blankets, and gushing: 'I can see you!'
Rob, was slightly less excited, however, as he questioned Cairo about what he had been shouting.
However, young Cairo, of course, had no idea what he was saying, happily responding: 'I said st!'
A serious Rob informed the young boy that he couldn't say that, firmly repeating the message as Cairo insisted: 'But I can say st if there's any disgusting things on the...' before the video cut out.
His mother had shared the video on Instagram, gushing: 'I've had this video for a min & it cracks me up!'
The expectant mother added: 'But overall I'm so happy & blessed to have Robert here willing to help teach King right from wrong.'