Ashlee Simpson Ross Says Son Ziggy, 11 Months, Is a 'Real Hit' with Her Other 2 Kids

Ashlee Simpson Ross's youngest son knows how to leave an impression on his siblings.

The singer, 37, caught up with PEOPLE at Wednesday's premiere of L.O.L Surprise! in Hollywood, California, where she opened up about the relationship between her three children.

Ashlee shares daughter Jagger Snow, 6, and Ziggy Blu, 1 this month, with husband Evan Ross, plus son Bronx Mowgli, 12, with ex-husband Pete Wentz.

Speaking about her newest little one, Ashlee says, "He's got a real sweet personality so he's a real hit."

"Jagger loves to entertain him," she adds of her daughter, who attended the movie premiere with her parents. "She likes to sing and dance for him."

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The star also dished on Ziggy's latest milestones, sharing that he is "standing on his own" and she thinks that "walking is coming" as he turns 1 later this month.

Ashlee can't believe how fast her kids are growing up, made clear in a sentimental post she recently shared in honor of Jagger's first day of kindergarten.

In the sweet photo, Jagger stands in her school uniform while holding up an "all about me" sign reading her age, grade, teacher's name and the date.

The chalkboard also featured some of Jagger's career aspirations, including her dreams of becoming an "artist, movie star and [to] walk on a runway."

"All the feels today ❤️😭," the proud mom captioned the picture on her Instagram Story.