So I doubt the fan recognised Dier's brother and started abusing him

I wouldnt recognise one of Chelsea's players' brothers from Adam.
More likely the fan was abusing Dier, unknowingly, Dier's brother was within ear shot and was like "Oi ya ****, thats my brother" and an altercation started.
Dier saw his brother having a punch up in the stands and run into the crowd to help him.
I can understand it I guess, but its still ****ing hilarious, and he will get shafted because of it
Why do Spurs always have meltdowns and lose their **** towards the end of the season when results go to ****? haha
Is this something thats bred into the club?