The couple, who met on the soap as Brooks works as a producer on the show, already have a son together who was born in October 2020.
Hardwick and Brooks revealed the news while appearing on Loose Women and were congratulated by the various hosts before being joined on set by their one-year-old son.
After revealing the pregnancy, Hardwick said: "It seems to have flown by this time. Quite a bit of morning sickness!"
The couple also revealed that the sperm donor is the same man as to who is the biological father to their son. They also said he would be open to meeting the children when they were 18.
Hardwick said: “When Teddy is 18 he can find out who his dad is and we’d massively back him. I’d love to meet him just to say, ‘Thank you so much for allowing us to be parents and giving us the most beautiful little boy.'"
Hardwick also wrote on Instagram: "We are super excited about our gorgeous news! I’m 20 weeks today and can almost rest a cup of tea on my bump."
The couple had previously discussed plans to have another baby after paying for IVF treatment for their son in 2020.
Hardwick has played Vanessa Woodfield in the Yorkshire-set soap since 2012 after previously appearing in The Royal and Heartbeat.
Hardwick and Brooks have been in a relationship since 2018, going public on National Coming Out Day. They married the following year at Elvis Presley's former home Graceland.
Loose Women airs weekdays at 12.30pm on ITV.
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