1. Mr. & Mrs. Lee: They both own a steel and construction company named 'Steel Innovate'. Their company is one of the top companies in the steel industry, hence their business is flourishing. Mr. Lee is the president, while Mrs. Lee is the vice president of the company. Even though they are rich, they never flaunt their money, and live a simple and humble life. They both really love kids so much, and its surprising that they had 2 sets of twins and 1 set of triplets. They have 7 kids in total. They are out of town most of the time due to business purposes, but they never neglect their kids and always are present for their milestones and achievements. If any of their kids needed them, they immediately drop their work and come to them. They also do not pressure their kids on their ambitions and let them do what they want. Mr. Lee is 51 years old and Mrs. Lee is 48 years old. 

First set of twins:

2. Lee Hakyeon (26 years): The eldest of the Lee siblings. He is elder twin of Lee Taekwoon, and is older than him by 5 minutes. He and Taekwoon took the responsibilty of taking care of their remaining siblings, when their parents are out of town. He is loud and keeps on nagging around the house. He is often the center of pranks played by his youngest siblings. His younger siblings often refer to him as 'mom' of the group. He adores his youngest sister Lee Haeun so much and, often competes with Taekwoon on who knows Haeun better. He is a dancer by profession, and goes by the stage name N. Though being the eldest son, he was never pressured to join the family business. He has been dating Kim Soyeon for a little over 2 years.

3. Lee Taekwoon (26 years): The younger twin of Lee Hakyeon. He is completely opposite in personality from Hakyeon. He is silent and talks only when necessary. The first impression he gives off is cold and scary, but once you know him deep down, he is actually caring and sweet. He is not great in expressing himself and often keeps to himself. He becomes soft and caring when he is with his youngest sister Lee Haeun. He works in his family's company, and is getting trained by his father to inherit his position. He has been dating Park Minseo for over 3 years. 

Second set of twins:

4. Lee Jaehwan (24 years): He is the elder twin of Lee Wonshik, and is older than him by 7 minutes. He is really loud and mischevious, hence connecting with his younger siblings easily. He is a popular singer and entertainer in Korea, and goes by the stage name Ken. He is known for his vocals and has performed in a lot of music