The Radfords, who have been dubbed "Britain's biggest family" due to the fact that there are just so many of them in the immediate family, has welcomed child No. 20.
Mrs Sue Radford, 42, gave birth to son Archie on Monday (Sept 18). He weighed about 3.8kg, the Sun reported on Thursday.
She gave birth at the Royal Lancaster Infirmary, where she said "all the midwives know me now".
She and her husband Noel Radford, 46, vowed that Archie will be their last child, and they said they are "happy to be finishing on a nice even number".
But she added, "It's strange knowing you're not going to have any more."
Mr Radford, who runs a pie company, will not be undergoing a vasectomy.
He had undergone one during her ninth pregnancy, but had it reversed after they decided to have more kids.
He said:"It was going to end at some point. We both think this is it. I feel sad in a way but now we can get on and enjoy the kids."
Baby Archie joins a brood which consists Chris, 28, Sophie, 23, Chloe, 22, Jack, 20, Daniel, 18, Luke and Millie, both 16, Katie, 14, James, 13, Ellie, 12, Aimee, 11, Josh, 10, Max, eight, Tillie, seven, Oscar, five, Casper, four, Hallie, two, and Phoebe, 13 months, reported The Daily Mail.
The couple sadly lost their son Alfie in July 2014, 23 weeks into the pregnancy, it added.
Mr and Mrs Radford are also grandparents - their eldest daughter Sophie has three children of her own.
The name Archie was chosen by their children, after they ran out of ideas for names.