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An Instagram video shared by the reality star's very pregnant fiancee shows Rob scolding his soon-to-be three-year-old stepson.

Blac who shares King Cairo with ex-fiance, Tyga, expressed her excitement at the fact that Rob is willing to teach her son right from wrong.

The video clip shows King playing around with a mobile phone with its camera on, recording him. Quite unexpectedly, King says, "Awww, S***t."

The Author George sock designer quickly responds saying, "What? What did you say?"

King goes on to repeat the swear word a couple of times, leading Rob to scold him calmly.

"No, you can’t say that. Don’t say that. That’s a bad word. Your mommy’s gonna get really mad at you.”

When King repeats the word again, Rob replies more forcefully,  “No! You can’t say that!”

Commenting on the cute video, Blac said:

“I’ve had this video for a min and it cracks me up!

“My favourite part is when Rob jumps out … look at his face … But overall I”m so happy and blessed to have Robert here willing to teach King right from wrong.”

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The couple is expecting their baby girl sometime in October and are super excited about it.

Earlier this month, King was reported to have gotten into trouble in school for swearing. Thankfully, Rob seems to be on top of the situation.