Song Jae Hyung and Song Jae Som are the younger siblings of Jae Gu Song. They are Fraternal twins. After the death of their father, their mother disappeared leaving Jae Gu to be the sole carer of the twins.
The twins look similar to their brother in appearance; having brown hair tinted with pink and large grey eyes. Although identical in facial features, there is stark differences in overall appearance with Som having long wavy hair and Hyung having short messy hair like Jae Gu. Both twins wear pink sweaters that are too big for them and jeans. Their school uniform consists of a yellow jacket and cap, white skirt and shorts and white shirts. Their pajamas consist of a blue tank top and shorts for Hyung and pink for Som.
The twins are initially portrayed as being disobedient and loud towards Jae Gu, demanding sausages for breakfast. They are aware of their living situation knowing how difficult it must be for Jae Gu to manage school life, working and their upbringing. Like all children they get excited by new things such as meeting new people. Understanding that Jae Gu does not have a lot of money or resources they do not ask for any special items such as takeaway food from a special restaurant they use to go to, saving up money instead to pay for their own meals and Jae Gu. They are often polite, but Hyung has been known for being rude or judgmental of the girls who want Jae Gu; ranking them on particular things that he think Jae Gu needs in a future wife. Between the two, Som is considered the more understanding and mature of them. Not wanting Jae Gu to be hurt or put out by her and Hyung. Hyung is immature but has been shown to understand Jae Gu's needs as a man more than his sister possibly can. According to Jung Gu, Jae Hyung is scary because he tallies Dal Dal's and Queen's points on who his the better candidate for his sister-in-law. But Jae Hyung technically cares for Jae Gu and hopes he gets the right girl.