Gisele Bundchen in Rio de Janeiro on June 5, 2012. Credit: CHRISTOPHE SIMON/AFP/Getty Images

Lil' Patriot -- and/or supermodel! -- on board!

After a couple weeks of speculation, Gisele Bundchen and husband Tom Brady are expecting their second child together, a source confirms exclusively to Us Weekly.

"Yes, she is pregnant," the source tells Us, adding that the Brazilian catwalker, 31, is "three months" along. "They are really happy!" the source says.

The baby-to-be will join big brother Benjamin, the couple's two-year-old son. Bundchen wed the handsome New England Patriots quarterback, 34, in April 2009; he also has a 4-year-old son, Jack, with ex-girlfriend Bridget Moynahan.

The Victoria's Secret catwalker begged out of the 13th annual Best Buddies Event in Hyannis Port, Mass. -- which Brady chaired -- over the weekend. But so far, even three months along, Bundchen barely has a bump to conceal. In a Boston park with Benjamin June 1, she offered a tiny glimpse of a growing belly in a loose-fitting beige top, which she accessorized with skin-tight pants, shades and a scarf.

Bundchen -- who has made a slew of controversial comments over the years about breastfeeding, her husband's 2012 Super Bowl loss (she blamed his teammates), her work ethic, the alleged dangers of sunscreen and more -- admitted in late 2010 that she wanted to grow her family.

"I want more kids for sure, but I don't know when," she told British Vogue, adding that "I have my hands full" with Benjamin and her stepson Jack.

"For Benjamin, his big brother is his hero," said the 5'11" stunner. "Jack comes in and Benjamin has a big smile. He wants to follow him around. Anything he does, he's just in awe of him like, 'Oh my God!'"