Why was Doodle considered to be a disappointment by Brother in the short story, "The Scarlet Ibis"?Need quote to support it.

The older brother in James Hurst's short story, The Scarlet Ibis, was hoping for a playmate with whom he could share his time: a normal brother. Instead he got Doodle.

I wanted more than anything else someone to race to Horshead Landing with, someone to box with, and someone to perch with in the top fork in the great pine behind the barn... I wanted a brother.

Doodle was so sickly that he was not expected to live, so his father built him a little coffin for when the time came. He was tiny and shriveled, and there was even the possibility that he was not "all there." Brother even considered smothering him with a pillow, but changed his mind when Doodle grinned at him one day. In the end, he proved to be "the craziest brother a boy ever had."