Ren was born and raised in Busan, South Korea. He has an older brother, Choi Minseok. He went to the audition held by Pledis Entertainment when he was in ninth grade and was quickly recuited afterwards. Ren attended Korea Art School and graduated in 2014. He is currently attending Inja University.
Prior to debut, Ren made numerous appearances in their labelmates' music releases as a member of Pledis Boys. He was a backup dancer in After School Blue's Wonder Boy and appeared in their label's Christmas release Love Letter, along with releasing their own music video for the song.
On March 15, 2012, Ren debuted as an official member of NU'EST. Ren and Minhyun had been gaining attention since their debut because of their heights and appearances. They appeared at the "F/W 2012–2013 Seoul Fashion Week" Runway as the models for designer Park Yoon Soo’s fashion show, “Big Park.” In the following year, Ren led the runway at the "2013 S/S Seoul Fashion Week". Along with his singing career, he has made appearances in several dramas. In 2013, Ren and Baekho had appearances in labelmate Uee's drama Jeon Woo-chi. In 2016, Ren played lead roles in the Japanese film, Their Distance.
First Round of Elimination
He started off being placed in group D due in the first episode. However, he was demoted to rank F after the weak re-evaluation performance. In the first live-audience challenge, group battle, Ren covered SHINee's Replay and got the highest vote among his team. He ranked #19 in the first elimination.
Second Round of Elimination
In the position-based challenge, he teamed up with Baekho and covered Black Pink's "Playing with Fire". He ranked #19 in the second round of elimination.
Third Round of Elimination
During the third challenge, Concept Evaluation, Ren was chosen as the center for his team to perform the song, Oh Little Girl, written by Kiggen and ASSBRASS. He ranked #24 in the third round of elimination.
Final Round of Elimination
In the last challenge, debut song evaluation, along with JR, Baekho and his team, he performed the song "Super Hot". He finished the competition ranking #20.
Many consider Ren as a progressive icon for his role in breaking gender conforming standards, as he has stated before that clothing does not define a person. He also modeled for a Chinese clothing brand that produces unisex or "genderless" fashions.
- Ren is a big fan of Lady Gaga
- He can play the piano
- His role model is Micheal Jackson.
- His ideal girl is a girl who “lies down looking at the blue sky above the green fields”
- He says the happiest time during his trainee days was when it was confirmed he was going to be a member of NU‘EST.