Avenging death of a brother is a running gag among villians in films...

... like these.

You've got Wah Sing Ku going nuts and trying to kill Riggs and Murtaugh to avenge the death of his bro at their hands at the end here, just like how in Die Hard you had Hans' henchman Karl spending most of the movie trying to kill John McClane to avenge the death of HIS brother--another of Hans' henchmen--at McClane's hands and Hans' own brother Simon going after McClane for the same reason in Die Hard 3.

Just goes to show that even action movie bad guys are often portrayed as having a very human side insofar they love their siblings and will go to great lengths for love.