The 48-year-old ‘Take That’ singer shared the news of their arrival to his fans on Twitter, writing: “Hello Dougie Bear Donald. He’s here and he’s beautiful.
“He arrived yesterday morning and we are over the Pluto.”
Donald announced in October 2016 his wife was expecting their second child.
“Guess what?” he wrote on Twitter at the time. “Me and Katie are happy to announce we will have our second child in Feb.
“Yay! No more sleep for another two years!”
Donald is also dad to 17-year-old Grace and 11-year-old Lola from his previous relationship. He and Halil started dating in 2011 and married in January 2015.
Congrats to the couple!