The Hanson drummer and his wife Kate welcomed their second child, daughter Junia Rosa Ruth, who arrived at 8 lbs., 7 oz. "We couldn't imagine a better Christmas gift than this sweet little girl," Hanson, 25, tells PEOPLE exclusively.
"In just the short time she's been here, she's enriched our family and our lives beyond measure," he adds. "We're looking forward to celebrating the season with our family and introducing her to everyone."
Baby Junia joins brother Shepherd, 2½, and a half-dozen cousins ranging from age 2 to 8: Zac's brother and bandmate Taylor has four kids while Isaac has two.
"We have no intentions to battle the Osmonds in any way," Zac has joked about his extended family's brood (who have joined the group on tour). "They can have the crown."
Adds Kate of the "super-fertile" Hanson headlines, "Honestly, we're pretty normal. We're three distinct families but people want to group us together!"
But as a band that's been performing together for well over a decade, it's difficult not to: Hanson just finished a sold-out tour to support their fifth studio album Shout It Out, which produced a hit video for the single "Thinking 'Bout Something".