The eldest Hanson brother and his wife Nikki welcomed a daughter on March 11 and are delighted to finally have a girl in the family, reported People magazine.
The 33-year-old musician said, "After more than five years of not having a baby in the house, having our first little girl is going to be fun. I know that Everett and Monroe are excited about being big brothers."
Isaac already has two children - Clark Everett, six, and five-year-old James Monroe.
Their band Hanson are best known for their smash hit 'MMMBop', which catapulted the long-haired brothers into the limelight in the late 90s.
Middle brother Taylor, 31, and his wife Natalie have five children - Ezra, 11, Penelope, eight, River, seven, Viggo, five, and 17 month old Wilhelmina - while youngest brother Zac, 28, and his wife Kate have three kids - Shepherd, five, Junia, three, and Abraham, five months.