Yang Hongseok 양홍석 was born on Sunday, April 17, 1994. He was born in the Chinese Year of the Dog along with group mate E'Dawn. Two other group members have birthdays near his so Jinho, Hongseok, and Yeo One are all the zodiac star sign Aries. He's 181 cm or 5'11½" tall. Five members, Jinho, Hui, Hongseok, Shinwon, and Yanan, all share the same blood type A.
Pentagon is a very multilingual group; all ten members can speak a second language in addition to Korean. The four members of the group who can speak English are Jinho, Hui, Hongseok, and Kino. Hongseok is also one of the five members in the group who can speak Mandarin, along with Jinho, Hui, Yeo One, and Yanan.
Hongseok lived in San Diego, California, USA, in Singapore, and in China when he was younger. He studies languages as a hobby.
His idol specialties are singing, acting, and writing lyrics. He also likes reading, working out, swimming, listening to music, and watching movies, especially Iron Man.
He auditioned for JYP Entertainment's 9th Audition Final Round in 2012 on the Model/Vocal team.
He became a trainee for YG Entertainment and competed on YG’s "Mix and Match" competition reality show that formed the group iKon.
He eventually moved to Cube Entertainment and was able to debut through Mnet's competition reality show "Pentagon Maker."
Hongseok modeled in ads alongside HyunA for her clothing line CLRIDE.n.