Vogue Williams and Spencer Matthews announced their are expecting their third child.
The presenter is due to give birth in spring 2022.
Speaking to Hello!, the presenter said: "It'll be the more the merrier."
The pair, who wed in 2018, are already parents to son Theodore and daughter Gigi.
"Theodore and Gigi absolutely love each other, they're always playing together.
"My sister Amber is my best friend and I want the three of them to be best mates."
She added: "Gigi doesn't have a clue she's getting a little brother or sister and I don't think Theodore minds.
"He doesn't really understand yet. If I ever mention the baby, he asks: 'Is it coming now?'"
On hearing the news, Matthews said: "It was a wonderful moment. I was delighted.
"We'd been trying, but I never expected it to happen as easily as it did. We're very lucky."
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