Johan Riley Fyodor Taiwo Samuel was born Wednesday at 5:01 p.m. in Los Angeles. "He is healthy, beautiful and looks just like his mother," according to the post signed by Seal.
In announcing the 8 lb. 11 oz. arrival, the new dad wrote, "To our children, a brother/ To our parents, a grandson/ To my wife and I, a son/ To our family, a blessing."
The baby is the third child for the supermodel and her second with the British singer, who is also father to the couple's 1-year-old son, Henry Guenther Ademola Dashtu Samuel. Klum's 2-year-old daughter, Leni, is from a previous relationship with Formula One manager Flavio Briatore.
Klum, 33, and Seal, 43, confirmed that they were expecting another child exclusively to PEOPLE in June.
From the start, Seal (real name: Seal Henry Olusegun Olumide Adeola Samuel) was like a father to Leni. "The arrival of any child brings you a lot of happiness," he told PEOPLE last year prior to the birth of Henry. "If we're lucky enough, we'll have more."
Klum, the German-born star of Bravo's Project Runway wholeheartedly concurs. In August she told Life magazine, "We want to have a lot of children. (Seal) always says that he finds me the most beautiful when I'm pregnant."
Last November, just two months after Henry was born, the proud papa told PEOPLE that he and Klum "try to spend as much time as possible together. There are days we never get out of our pajamas. We play with the kids in bed, watch TV, cook, hang out."
Added Klum: "Our kids are a constant source of amusement."