The Hanson brothers' brood has gotten even bigger.

On July 1, Isaac Hanson and his wife Nikki celebrated the arrival of their second son, James Monroe Hanson, in the family's hometown of Tulsa.

Baby Monroe weighed in at 8 lbs., 11 oz., and joins older brother Clark Everett Hanson, 1. Both boys go by their middle names.

"The addition of Monroe to our family is incredible and exciting," Isaac, 27, the eldest of the rock trio Hanson, told PEOPLE. "With Monroe and Everett being so close in age, it will be great to watch them grow up together."

"Two little boys is going to be twice the fun," he adds.

Isaac's youngest brother, Zac, and his wife Kate just welcomed their first child, John Ira Shepherd Hanson in May. And middle brother Taylor has three children, for a total of six kids among the bandmates.

After undergoing rib resection surgery in December following a pulmonary embolism, Isaac has had a clean bill of health since January.

He'll hit the road on Hanson's 8-week tour for their album, The Walk, of the U.S. and South America this fall.

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