#1 The Undertaker and Imposter Undertaker at WWE SummerSlam 1994
Throughout his career, The Undertaker was believed to be the brother of fellow WWE star Kane. This was because Paul Bearer was able to tell quite a believable story regarding the two men's upbringing and they then went on to have a fantastic feud.
In reality, Kane and The Undertaker are not related, but The Deadman has been able to feud with his cousin as part of the rivalry in WWE between The Phenom and the imposter Undertaker back in 1994.
Undertaker was missing after his loss to Yokozuna so Ted DiBiase managed to find "The Undertaker" and convinced him to join The Million Dollar Corporation. When the real Undertaker returned and defeated the imposter Undertaker at SummerSlam later that year, the storyline was dropped and Brian Lee was released from WWE.
Throughout the feud, there were many fans that noted the fact that both men looked very similar and this was because the man behind The Undertaker and the man behind fake Undertaker Brian Lee were cousins in real life.