Kim Ji-yeon’s Jewelry Box: Acting-prodigy sisters Do Yeong-seo and Kim Sia, Netflix’s two ‘granddaughters’

The Coupang Play series 〈The Affair was Just the Beginning〉, which has released four episodes so far (hereafter 〈The Affair〉), is a series whose appeal lies in peeling back its many layers one by one. Blending cynicism and wry laughter, satire and boldness, the series never loses energy as it shifts focus: first it seems the affair is the problem, then the children, and then again the adults.

As Kyung-hee (Park Kyung-hee) says, "It would have been better if it had been just an affair." In 〈The Affair〉, an influencer couple who sell an image of domestic bliss become entangled with a doctor couple locked in a divorce case, exposing not only problems involving their children but also the petty ambitions and inferiority complexes of parents desperate to save face through their kids. As the adults in this distinctly Korean black comedy try to untangle the mess they made, the story keeps returning to the children.

Episode 3 of 〈The Affair〉 shifts its focus to the children. In the series, the kids of the two couples expose the adults' desires and hypocrisies and reinforce the series’ black-comedy tone. Min-seo, the daughter of Su-jeong (Jo Yeo-jung) and Bo-seong (Kim Jae-chul), played by Do Yeong-seo, is the show’s quiet bombshell. Min-seo becomes the subject of a custody dispute between divorcing parents and is a child who learned early to hide her emotions. She wants to study art, but she is stifled every day by her physician mother’s interference and opposition. Then she befriends Ye-ji, the daughter of neighbors Kyung-hee and Jae-hong (Kim Ji-hoon), begins to open up about her bottled-up feelings, and soon the two become secret lovers.

Min-seo's storyline in 〈The Affair〉 brought to mind Gil Jae-young (Kim Sia) in the Netflix film 〈Gilboksoon〉. As Min-gyu (Seol Kyung-gu) says, "When a secret forms, a wall slowly appears," and Jae-young, the teenage daughter of killer Gilboksoon (Jeon Do-yeon), who disguises herself as an office worker, carries her own secret: she has a girlfriend. Behind parents who awkwardly guess, "Does our daughter have a boyfriend?" when they see her constantly on her phone at the table, the children are living double lives of their own. As Gilboksoon puts it, "Killing someone is simple compared with raising a child"—looking into your child’s inner life is a more complicated territory than murder or affairs. That idea—that raising children is the hardest task adults face—runs through both 〈Gilboksoon〉 and 〈The Affair〉.

Coincidentally, the actresses who played Jae-young in 〈Gilboksoon〉 and Min-seo in 〈The Affair〉 are sisters. Kim Sia, born in 2008, and Do Yeong-seo, born in 2010, may well become the sibling pair widely regarded as acting prodigies representing Korea. The older sister, Kim Sia, who became famous before her younger sister, made a striking debut as the lead in 〈Miss Baek〉. At age 10 she beat a 600-to-1 competition to win the role of abused child Ji-eun, and she moved audiences by conveying a child's fear and wounds more through her eyes and expressions than through dialogue—from a face hardened by abuse to the moment she finds warmth and rescue in Miss Baek (Han Ji-min). As an aside, Do Yeong-seo, Kim Sia’s younger sister, also appeared as the young version of Miss Baek (Han Ji-min).

Kim Sia, who captivated director Lee Ji-won with what he described as "eyes that knew everything" in 〈Miss Baek〉, will return to Korean theaters this September in Lee’s new film 〈Bi-gwang〉. Kim Sia plays Dong-ju, a girl driven to the brink after a friend’s death leaves her under suspicion. Dong-ju suddenly enters the life of Jung-gu (Ryu Seung-ryong) and becomes part of his household; she becomes embroiled in the death of a middle-school girl in Ulimcheon and finds herself the focus of public suspicion, facing a vast truth alongside the family trying to protect her. As she did in 〈Miss Baek〉, Kim Sia will likely portray Dong-ju’s complex psychology—the anxiety, confusion, despair and fear of a life upended by an unexpected event—with the same compelling clarity and instinctive power.

What’s interesting is how different the sisters’ acting styles are. In the midst of the adults’ messy, petty battles for desire and status in 〈The Affair〉, Do Yeong-seo’s Min-seo often appears outwardly unshaken and composed. Even while the adults bustle around, each hiding their own secrets, Min-seo looks as if she is keeping her distance. Her seemingly indifferent face only makes viewers more curious about her inner world.

Do Yeong-seo is an actor who makes you imagine a character’s interior without exaggerating her emotions. That approach was on clear display in the Netflix series 〈Eun-joong and Sang-yeon〉. Do Yeong-seo played the young Ryu Eun-joong, portraying the childhood of the character who later becomes the Eun-joong played by Kim Go-eun. Rather than mimicking adult emotions, she showed jealousy, admiration, hurt and longing in ways true to a child of that age, naturally connecting the younger Ryu Eun-joong’s arc to the adult’s emotional line. As director Cho Young-min of 〈Eun-joong and Sang-yeon〉 said—he doesn't favor the stagey child-actor style that looks learned in academy classes—Do Yeong-seo had none of that 'self-conscious, obviously trained' quality.

Despite different methods and styles, the sisters share one trait: they show up in Netflix projects with unusual frequency— they’ve become something like Netflix regulars. Kim Sia and Do Yeong-seo (who formerly worked under the name Kim Bo-min) both appeared in the Netflix series 〈The Silent Sea〉, and they made a brief joint cameo in the Netflix film 〈Good News〉 (2025). Beyond that, Kim Sia has appeared in Netflix projects from 〈Kingdom: Ashin of the North〉 to 〈Sweet Home〉, 〈Gilboksoon〉, and 〈Gi-ri-go〉. Do Yeong-seo has credits in the Netflix films 〈Carter〉 (2022) and 〈Revelations〉 (2025), the Netflix series 〈Jongmal-ui Babo〉 and 〈Eun-joong and Sang-yeon〉, and the forthcoming Netflix film 〈Bokjik Gyeongchal〉. At this point, you could almost call them Netflix’s own 'granddaughters.'