The couple say they are 'eternally grateful' to NHS staff after the birth of their son, which was announced on BBC Look North last Friday.
Broadcaster Harry hit back at critics in June following the announcement that he and his wife were expecting a baby.
The couple, who live in York, announced the birth of Hamilton on Twitter today and shared two adorable pictures, thanking staff at Sheffield's Royal Hallamshire Hospital.
Helen Gration said: "Our family of four is now five!
"We‘re v happy to announce the arrival of Hamilton! Heartfelt thanks to @EmmaFerriman & team at Sheffield’s Jessop Wing, #RoyalHallamshire & Paula Schofield & team.
"Norfolk & Rivelin wards’ staff are outstanding #NHS. Eternally grateful."
The couple already have two children, 16-year-old twin boys Harvey and Harrison, and Helen said she realised she wanted to try for another child with their teenage boys ready to leave for university soon.
A fertility consultant told Helen she could have another baby, despite her age, but said she would need an egg donor due to hers being “too old and viable”.
The couple started looking for an egg donor back in January 2018 and were advised to look into a clinic in Cyprus due to the lengthy process of finding a donor in the UK.
The couple travelled to Cyprus to have the IVF done and were delighted when they found out it had been successful.