London:  Elton John has confirmed that his son will undergo a DNA test to determine whether the singer or his partner David Furnish is the tot's biological father.

The couple welcomed baby Zachary over Christmas with the help of a surrogate mother. Elton also revealed that they both contributed sperm samples to the fertilization process.

"Zach will have to know for his medical records. If it's David, I'd be very proud. It wouldn't matter to me – and vice versa," the 64 years old singer said.

John also said their surrogate mother sent them breast milk via courier during their first four months after his birth.