The Apprentice star's son Donald Trump, Jr.'s wife Vanessa gave birth to the couple's third child, Tristan Milos, on Sunday (02Oct11).
The baby boy will join Donnie John III, two, and Kai Madison, four.
Taking to his Twitter.com account to share the baby news, Trump, Jr. wrote, "Mom and baby doing great! He can’t wait (to) meet his big brother & sister.”
And business tycoon Trump is thrilled by the latest addition.
He tells People.com, "I am delighted that Don and Vanessa have a beautiful new member of their growing family.”
This is Trump's fourth grandchild - daughter Ivanka gave birth to her first child, Arabella Rose, in July (11).