Two brothers

Two brothers enlisting in the Army were getting their physicals. During the
inspection, the doctor was surprised to discover that both of them possessed
incredibly long, oversized penises.
"How do you account for this?" he asked the brothers.
"It's hereditary, sir," the older one replied.
"I see," said the doctor, writing in his file. "Your father's the reason for
your elongated penises?"
"No sir, our mother."
"Your mother? You idiot, women don't have penises!"
"I know, sir," replied the recruit�, but she only had one arm, and when it
came to getting us out of the bathtub, she had to manage as best she could."