The History of the Moon Siblings: ASTRO's Moonbin and Billlie's Moon Sua

Written By Jacob Leung

With many K-Pop idols making their debut each year, the K-Pop industry has seen its fair share of idol siblings.

Perhaps older fans will think of sisters such as former Girls’ Generation’s Jessica Jung and f(x)’s Krystal Jung, brothers such as BOYFRIEND’s Youngmin and Kwangmin, or brother and sister siblings such as Chanhyuk and Suhyun from the duo Akdong Musician. 

Newer fans might be familiar with former IZ*ONE’s Chaeyeon and ITZY’s Chaeryeong, ONEUS’s Xion and ONEWE’s Dongmyeong, and TXT (Tomorrow x Together)’s Hueningkai and Kep1er’s Huening Bahiyyih. 

Among these idol siblings are ASTRO’s Moonbin and Billlie’s Moon Sua: two idols who have waited many years to share the stage together. In celebration of their recent special stage on KBS Music Bank, let’s delve into the history of Moonbin and Moon Sua’s journeys as idols. 

2000s - Early 2010s

Moonbin began his career as a child model and actor, landing roles in popular pieces of media. In 2006, he starred in TVXQ’s “Balloons” music video as a tiny U-Know Yunho. Three years later, he appeared as a younger version of a star once again,  playing the younger version of Kim Bum’s character, So Yijung, in the K-Drama Boys Over Flowers. 

Moon Sua also entered the entertainment industry at a young age. In 2011, two years after she started training at YG Entertainment, she appeared in GD & TOP’s “Knock Out” music video. 

This music video gave exposure to YG Entertainment’s “Future 2NE1” lineup, which Moon Sua was a part of. Other members of Future 2NE1 included fromis_9’s Seoyeon and soloists Youha and Roya.  

The Mid-2010s

Moonbin continued modeling while being a trainee at Fantagio. By the mid-2010s, Moonbin partook in Fantagio’s “iTeen” program and secured his spot as a member of ASTRO. 

Prior to ASTRO’s debut in 2016, the group released many contents to generate interest. The largest of these projects was To Be Continued, a web drama that spanned 12 episodes and ran from August to September 2015. After months of anticipation, ASTRO finally made their debut with Spring Up and its accompanying music video for “HIDE&SEEK” on February 23, 2016. 

ASTRO released six mini-albums, two special albums, and one full-length album throughout the 2010s. 

Not too long after To Be Continued finished airing, Moon Sua showcased her talents through Unpretty Rapstar 2. From September to November 2015, alongside notable female stars such as Hyolyn, HEIZE, and Yezi, she competed to see who was the best female rapper. 

Her most notable song from the show was “Who Am I,” featuring Akdong Musician’s Suhyun. Despite being the youngest participant on the show, she managed to place fourth. Moon Sua eventually left YG Entertainment in 2019, but many were anticipating when, and where, she would make her debut.  

Early 2020s

Moonbin continued acting as 2020 arrived. After years of playing guest and supporting roles, 2020’s Mermaid Prince saw Moonbin in a central role. He also undertook additional activities, getting the chance to host MBC’s Show Champion with fellow ASTRO member Sanha and VERIVERY’s Kangmin starting early 2020. 

The chemistry that he shared with Sanha during this hosting period inspired the two to form ASTRO’s first sub-unit: MOONBIN&SANHA. MOONBIN&SANHA released their debut EP, In-Out, on September 14, 2020 with the title track “Bad Idea.” 

Moon Sua created a new start as part of Mystic Rookies, a temporary name for MYSTIC STORY’s then-upcoming girl group. She participated in multiple 2020 “Listen Stages,” livestreams posted on Mystic Story’s official YouTube channel, as a way to showcase the talents of Mystic Story artists. 

After 12 lengthy years, Moon Sua finally made her debut as a member of Billlie on November 10, 2021. Billlie’s original lineup consisted of Moon Sua, Suhyeon, Haram, Tsuki, Siyoon, and Haruna before re-debuting and adding Sheon (Girls Planet 999 contestant Kim Suyeon) on November 27, 2021. 

Moonbin supported his sister and her group multiple times during this initial period. As a Show Champion host during their the Billage of perception: chapter one promotions, he was able to interview and congratulate them. 

Additionally, Moonbin also applied for a Billlie fansign and won, granting him a chance to speak to Moon Sua and the rest of the members. An ASTRO vlog and Billlie vlog documented both perspectives of the video call. 

ASTRO wrapped up 2021 releasing their second full-length album and their eighth EP  while Billlie capped the year off with their winter digital single, “Snowy Night.” 

In late February 2022, Billlie released their second EP the collective soul and unconsciousness: chapter one with the title track, “GingaMingaYo (the strange world).” This promotional period eventually overlapped with MOONBIN&SANHA’s, who were promoting “Who,” the title track of their second EP Refuge. 

All these promotions and interactions lead up to their special stage in June 2022–the long-awaited collaboration between the two siblings. 

Their Special Stage

On June 24, 2022, the two performed a cover of “Candy In My Ears,” originally by legendary vocalist Baek Jiyoung featuring Taecyeon of 2PM. 

Despite Moonbin being known for dance and Moon Sua being known for rap, this special stage allowed them to display their additional roles within their groups. Both showed their skills as lead vocalists in their respective groups and exuded many charms. In the second verse of the song, they briefly switched roles, with Moon Sua taking Taecyeon’s part and Moonbin taking Baek Jiyoung’s part, showcasing Moon Sua’s deeper tone and Moonbin’s beautiful falsetto. 

The performance featured cute sibling moments, with Moonbin taking his time to pat his younger sister on the head (much to her annoyance) and Moon Sua acting cute towards her older brother during the “ending fairy” shot. 

In the following days, praise arose among AROHAs (ASTRO fans), Belllie’ves (Billlie fans), and other K-Pop listeners alike. Combining the performance views from the KBS World TV and KBS Kpop YouTube channels, their special stage has amassed over three million views and counting. Some fans expressed their gratitude to the KBS Kpop channel directly: through YouTube’s “Super Like” function, pleased viewers gave the channel a small monetary donation. 

What’s New?

ASTRO and Billlie both head for London in July: ASTRO will be part of HallyuPopFest in London on July 9 while Billlie will headline the MIK (Made in Korea) Festival on July 30.

Additionally, some members of ASTRO will attend the Australian portion of HallyuPopFest as well. Jinjin, Moonbin, Rocky, and Sanha will perform in Sydney on August 14. 
While no music is currently on the horizon for ASTRO, Billlie has some music-related work coming up. Billlie will release a remake of “Pat Bingsu” (팥빙수, Red Bean Bingsu), a song originally sung by MYSTIC STORY founder Yoon Jongshin. The single is part of the “track by YOON” project at MYSTIC STORY. “Pat Bingsu” releases on July 14.

Edited by Meighan Peters

About the Author
Jacob Leung is a Canadian writer who became a K-Pop fan in 2017. Five years later, he still finds new and exciting facets to explore in the industry. When he’s not jamming out to K-Pop, he can be found discussing video games, cartoons, and other forms of media on his personal blog and Twitter account.