Jared Kushner and Ivanka Trump

Ivanka Trump and husband Jared Kushner welcomed a baby boy on Monday. 

Joseph Frederick Kushner was born Monday at 9:54 p.m. "We just welcomed a beautiful & healthy son into the world. Jared, Arabella and I couldn't be happier!" Trump tweeted. The couple are already parents to daughter Arabella Rose, 2. 

Joseph is the name of Kushner's grandfather, whom Trump praised in a post on her Tumblr Tuesday. "His indomitable spirit, his sense of family, and his work ethic are the values we hope to hand down to our son." Frederick is the name of Trump's grandfather "who was a builder not just of tens of thousands of homes throughout this city, but of a tight-knit family that honors to this day the traditions he established," she wrote. "We are honored to name our son after these two distinguished men. We feel so blessed with the newest member of the family!"

PHOTOS: Celebs with doppelganger kids

The Celebrity Apprentice mentor's father Donald Trump also shared his joy on Twitter: "Thanks to all for the wonderful congratulation sent to me on the birth of Ivanka's little boy - so nice!"

The latest addition to Trump and Kushner's family comes 11 days before the couple's fourth wedding anniversary.