Dressed in head-toe-black, former Essex star Mark was among the crowd at the City Pavillion in Romford to watch the big fight, which had been hyped heavily on TOWIE.
It ended when Lewis was knocked out in less than a minute, although he did attempt to struggle on.
A thrilled Mark tweeted: "Tonight my big cousin did me proud !! @elliottwright_ the name is WRIGHT we don't lose !! Love him to bits #wright (sic)."
However, he also gave props to Lewis, saying: "Well done to @lewis_bloor for getting up and trying to continue. It takes a man to be in there in the 1st place. Well done mate #warrior."
Meanwhile, Lewis was a gracious loser, tweeting: "Well done @elliottwright_ better man won! ko'd me 40 seconds in such strength i just couldn't live with it."
He then joked: "Being told 30 seconds now cant really remember much if im honest!"
Lewis continued: "For the record anyone standing after one of @elliottwright_ straight rights is welcome to the keys to my house... To add, I will fight again, boxing is a great way to keep fit and focused day to day, a lot went in 2 that night. Gutted didn't go the distance."
Got an iPad or iPhone? Reveal Mag is specially designed to fit! Find out more here