As it turns out, Siri's older sister's name is Directory Assistance.
I learned that not from Apple's intelligent mobile assistant, but from Marchex's John Busby, whom was just explaining all the voice-based things people still do with their mobile phones, even the super smart ones we might describe as intelligent.
"Siri does have an older sister," Busby said, "and her name is directory assistance."
Busby, of course, was referring to the good-old fashioned phone operators or automatons whom human beings call to get information over their phones. You know, what kids call "the 411" today? Imagine that, some people still actually do it by dialing 411, or some version of that numeric input.