Zac Hanson Welcomes Baby No. 4 -- Find Out Her Classic Name!

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Zac Hanson is now a father of four!

The Hanson drummer and his wife, Kate, have welcomed a new baby girl into their family. Mary Lucille Diana Hanson was born on Saturday, Aug. 6.

"It is such an inspiration to meet her and to imagine all of the adventures we will take together as a family of six," the 30-year-old musician said in a statement to ET, noting that the family was "overjoyed" about the new arrival.

WATCH: Hanson Working on Seventh Studio Album, Promise New Music 'No Matter What' 

Courtesy of Zac Hanson

Like many of her family members -- Isaac and Taylor Hanson included -- Lucille will go by her middle name. The moniker proves to be especially sweet for longtime fans of her dad's band, remembering their song "Lucy" from 1997's Middle of Nowhere.

WATCH: Andrew McMahon Talks Working With Hanson 

The name Diana also holds special meaning for the family: it comes from Zac's mother, Diana Hanson.

Zac and Kate celebrated 10 years of marriage in June of this year. Rounding out their family are sons John Ira Shepherd, 8, George Abraham, 2, and daughter Junia Rose Ruth, 5.

In a November interview with ET, Zac and his famous brothers joked about the next generation following in their musical footsteps.

"There is a lot of music in the Hanson family," Taylor said. "I mean, it's just in the gene pool."

"It’s like mono,” Zac echoed. "Everybody's got it, you just don’t know when it's going to come out."

Believe it or not, 2015 marked the 20th anniversary of Hanson's breakout single, "MMMBop." The band got nostalgic in an interview with ET, opening up about why they're so "proud" of the song.

"Songs like 'MMMBop' actually talk about how things come and go and how you have to be able to hold onto relationships and people that matter… it stands the test of time I think because it's actually saying something, it always was," Taylor said.

See the interview below.

WATCH: Hanson Looks Back on 20 Years of 'MMMBop,' Talk Paving the Way for Taylor Swift