What is kane and undertaker really brothers?

Kane and The Undertaker, both professional wrestlers in WWE, are not actual biological brothers. However, in storyline, they are half-brothers and have been involved in various storylines throughout their careers in WWE. The storyline of their relationship began in 1997 when Kane was introduced as The Undertaker's long-lost younger brother seeking revenge for being left to burn in a fire years ago. Despite the storyline being fabricated, Kane and The Undertaker have maintained their on-screen relationship for many years, even forming a tag team known as The Brothers of Destruction.