What is the cause of death of his brother was it shown?

I shot that muthafucka twenty three times in his balls…but the author won’t show that part lol

Wasn't he sick? Like he had an illness since he was a child? That might be the reason but Idk

I think he had cancer or some other terminal disease

It was not exactly shown yet. He had poor health but it never said he died from his sickness.