What impact did Robert Ross' Uncle have on his life? Why was it singled out in page 164 out of all the other deaths?

On page 164 the last paragraph of part 4 The narrator tells us how many people have died and singles out 3 deaths which were death by streetcar, bronchitis and one who died with her Rabbits. Each one of them had a mental toll on Robert's life. I fail to understand why Robert's uncle's death was singled out.