How old is Tom's Granny?

Two guys are driving down 5th Avenue in Manhattan when they come up to a red light. The guy driving slams the gas pedal and they go zooming past the red light. His friend looks at him and says, "Hey, you just went through a red light." The guy driving says, "Don't worry about it. My brother does it all the time." So they keep driving and they come to a second red light. The guy driving slams on the gas pedal and zooms past another red light. His friend is pretty mad, looks at him and says, "Hey man, you just went through another red light. What the heck are you doing?" The guy driving tells his friend, "Don't worry about it. My brother does this all the time." They come to a third red light and the guy driving slams on the gas, zooming past the red light. His friend starts screaming at him, "What the heck? You're going to get us killed! Pull over and let me out." The guy driving screams back at him, "I'm telling you: don't worry about it. My brother, he does it all the time." So they keep driving and they come to a green light. The guy driving slams on the brakes. His friend looks at him and says, "Are you out of your mind? What the heck is wrong with you? You go flying past three red lights, almost getting us killed, and then you slam on the brakes when you have a green light?" The guy driving looks at his friend and says, "I had to stop; my brother might have been coming."