Their son was delivered Thursday 4 September and the former Girls Aloud star announced the happy news on Twitter, telling followers: "Our beautiful baby boy Bobby arrived yesterday afternoon 04/09/14 he's perfect"
Our beautiful baby boy Bobby arrived yesterday afternoon 04/09/14 he's perfect 😍👶🍼— Kimberley Walsh (@KimberleyJWalsh) September 5, 2014
Her bandmates wasted no time in sending their congratulations.
Cheryl Fernandez-Versini replied to Kimberley's tweet with: "He really is, he's perfect!" while her tweet included lots of smiley face emojis.
Nicola Roberts also became involved in the conversation adding: "I can't believe he's here".
@KimberleyJWalsh He really is 😭😍😍😍😍😍 he's perfect ! ❤️👶👼🍼— Cheryl (@CherylOfficial) September 5, 2014
Kimberley first let on that she was expecting in February, describing the news as "crazy”.
“I can’t believe I’m actually going to be a mother and there’s this thing inside me, waving its hands around and wriggling. I’m so excited," she said. "I feel like I’ve had to live in a selfish way for too long and now I’m looking forward to giving that up for somebody else.”
The pregnancy wasn't without incident. In March she was forced to reassure fans that her "little munchkin" was fine after falling and breaking her wrist.