Carson Daly: Why My Son Is My Secret Weapon

"[Siri] tries her tricks and then we looked at Jackson and we go, 'Jack, come here, make her stop crying!' and Jackson comes over and goes, 'Hi baby sissy!' and he kisses her and she lights up."

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All Carson Daly‘s shushing and swaying couldn’t keep his daughter Etta Jones quiet on a recent holiday flight cross country.

Fortunately, Daly and his girlfriend Siri Pinter come equipped with a backup plan: big brother Jackson James, 3½.

“Etta was crying on the flight home from New Year’s Eve in New York. I looked at Siri and I have my finger in her mouth — she won’t suck on that — I’m out of my tricks,” The Voice host, 39, told PEOPLE at NBC’s Television Critics Association party Sunday in Pasadena, Calif.

“Siri tries her tricks and then we looked at Jackson and we go, ‘Jack, come here, make her stop crying!’ and Jackson comes over and goes, ‘Hi baby sissy!’ and he kisses her and she lights up.”

With the 4-month-old “locked into” Jackson, Daly admits his son has completely stepped up to the plate when it comes to caring for his sister.

“I almost forget she’s in the house sometimes and Jack reminds me, ‘Dada look out for Etta!’ He’s like an adult,” the proud papa jokes.

But while Etta’s brother may be shining in the sibling spotlight, it’s her great grandparents who served as inspiration behind her moniker.

“Etta is Siri’s grandmother’s name, Henrietta. It was an homage to her. When we go to visit Siri’s mom in Minnesota, we stay down in her basement and it’s where her grandparents lived,” Daly explains, adding Jones is both his middle name and his mom’s maiden name.

“We wanted Etta to have some of Siri’s family. Etta Jones was also a great jazz singer.”

— Anya Leon with reporting by Aili Nahas