Isaac and his wife, Nikki
Isaac Hanson and his wife, Nikki, are expecting their second child, Hanson tells PEOPLE.
"Nikki and I are so very excited about the new addition to our family," he says. "We can't wait to meet him or her."
The eldest of the Hanson clan, Isaac, 27, and Nicole, 24, his wife since September 2006
, also have a 10-month-old son
Their new addition will also have an instant playmate – Isaac's younger brother Zac and his wife, Kate, are expecting their first child
Before Isaac's daddy duties increase, he'll stay busy on the road: Hanson will play two shows at Austin's SXSW, then they'll kick off "The Walk" tour April 9 (for more tour info, visit www.hanson.net