Two Chihuahua dogs petrified of leashes, how can i earn their trust so i can walk them.?

My aunt has had the dogs since they were puppies, but my cousins NEVER walk them. every time i go over i try to take them on walks. Lucy the female, takes off running and cryin non stop, then hides in her house after i remove the leash, and wont come out of there until the next day. Ricky the male, simply wont budge. One has to drag him, but still its no use. I really love these dogs. They love my attention, but they are afraid of the leash. What can i do to cure them of this paranoia, and get them to walk with me without forcing them?