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The family announced the news on their official Facebook and Instagram pages, where they shared a photograph of the new arrival's hand, writing: "We welcomed our beautiful baby girl into the world on Friday night.
"We're all so in love with her."
They also told fans to watch out for a vlog, which would be online soon.
The Radford family are well known in the UK after they first appeared on Channel 4 documentary series 15 Kids and Counting - which was followed up with later instalments as the brood grew.
Sue, 45, and husband Noel, 49, have 22 kids in total:Chris, 30, Sophie, 25, Chloe, 23, Jack, 22, Daniel, 20, Luke, 18, Millie, 17, Katie, 16, James, 15, Ellie, 14, Aimee, 13, Josh, 12, Max, 11, Tillie, nine, Oscar, seven, Casper, six, Hallie, three, Phoebe, two, Archie 18 months, and Bonnie, one.
Sue also sadly suffered a miscarriage at 23 weeks in 2014.
Second-oldest Sophie also has three kids of her own, making Sue and Noel grandparents as well.
The family document their life on social media, with 237,000 followers on Instagram and more than 333,000 likes on their Facebook page.
They also share vlogs on YouTube, having given regular updates about their 22nd child throughout the pregnancy.
In October they shared footage from their 12-week scan, which took place at the end of September.
"We're going to have a little peek at the new little Radford," Sue said in the video.
Three of their 21 children were also watching their unborn sister on the screen in 2D and 3D, and were also able to hear her heartbeat.
Sue reckoned she was having another boy, but Noel wasn't so sure.
Speaking about the scan, he said: "One minute it looked like a girl, the next minute it looked like a boy, so we're not sure."
Revealing plans to do a gender reveal in the coming weeks, Noel added: "It's a long way to go yet but yeah... it's a good Christmas."
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