Lewis Singwah Tan was born in Salford, England, and was raised primarily in Los Angeles, living also in France, Thailand, Spain, and China.
Tan identifies as half-Asian, half-British. His father, Philip Tan, is a martial artist, actor, and stunt coordinator of Chinese descent from Singapore.
His mother, Joanne, is British and a retired fashion model from the UK. His family moved to Los Angeles when his father was hired as a fight coordinator for Tim Burton's 1989 film Batman. He is the eldest of four brothers. His younger brother, Sam Tan, is also an actor.
His youngest brother, Evan Tan, is a photographer based in LA whose work has been featured on the art for songs from artists such as Kali Uchis and Zack Villere. Tan's father trained him in martial arts from a young age. He also began training in theatre as a young teen, leading many plays. He studied performing arts with coach John Kirby