Use a dictionary to map the first names to the tuples you have.
names = { "john": (“doe”, “13-apr-1985”),
"clark": (“kent”, “11-jan—1987”),
"bruce": (“wayne”, “05-sep-1988”)}
user = raw_input(“What is your name?”)
if user in names.keys():
print “Your last name is: “ + names[user][0]
print “Your date of birth is: “ + names[user][1]
else:
print “I don’t know you.”
To make this even more pythonic and easier to work with, make a nested dictionary:
names = { "john": {"last": “doe”, "birthdate": “13-apr-1985”},
"clark": {"last": “kent”, "birthdate": “11-jan—1987”},
"bruce": {"last": “wayne”, "birthdate": “05-sep-1988”}}
user = raw_input(“What is your name?”)
if user in names.keys():
print “Your last name is: “ + names[user]["last"]
print “Your date of birth is: “ + names[user]["birthdate"]
else:
print “I don’t know you.”
As a side note, you probably want to trim any leading whitespace off the input while you're at it.
...
user = raw_input(“What is your name?”)
user = user.strip()
if user in names.keys():
...