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Brody, who was 8 lb., 2 oz., joins the couple's first child, 4-year-old sister Reece Viola.
Hamilton, 43, who also has a 12-year-old daughter from a previous marriage, has said Reece Viola faces some adjustments.
"She is the center of the universe right now, and when the next one comes along it's gonna rock her little boat a little bit," he said in August. "But it'll be great. ... It will be great for her."
Reece, 37, stayed in top shape during her second pregnancy by playing competitive beach volleyball last summer and swimming.
Reece first announced she was pregnant on the Today show for which she's also a special correspondent.
