In reality, Dumbledore's relationship with his brother was not nearly as bad as he had made it sound.
At the very least, Aberforth did not refuse to let the homeless Reed and Tom stay.
In Reed's view, Aberforth was simply all bark and bite when it came to his older brother. Though his words toward Dumbledore were never kind, he still conscientiously carried out whatever tasks his brother entrusted to him.
Chapter 34