Donald Trump Jr and Vanessa Trump on May 3, 2012 in New York. Credit: Craig Barritt/Getty Images

Four times the fun for Donald Trump Jr. and Vanessa Trump!

Donald Trump's businessman son and his bride of seven years welcomed their fourth child -- a baby boy -- on Sunday, Trump Jr. tweeted.

"It's a BOY!!! Vanessa and baby are doing great," the proud dad confirmed on the microblogging site.

The family's new arrival joins older siblings Kai, 5, Donald III, 3, and Tristan, 11 months.

Shortly after confirming her fourth pregnancy in May, Trump's La Poshett handbag designer wife told Us Weekly they were "so blessed to be able to have another child to add to our happy, growing family."

Married since 2005, the couple said that their two oldest children were over-the-moon about getting a sibling.

"Tristan . . . doesn't know what's going on," Donald told Us. "But Kai and Donnie are so excited! They're so involved with Tristan and love helping me feed and change him--so they're looking forward to having another baby around!"