2. Kane
The Undertaker's history with Kane is long and storied. He first tried to kill his brother when they were just young. He admitted to starting a fire that left Kane needing to wear a mask. Years of feuding then took place in which both men would attempt to murder the other. Everything from setting each other on fire to burying each other alive - both men did everything to try and hurt the other. It's definitely a messed up family dynamic, as we've also seen them as friends and tagging together as recently as 2013. The Brothers Of Destruction truly are what you'd call dysfunctional.