Time, patience, and respect. Trust must be earned slowly.
I would start by determining how far away the birds will tolerate your hand without backing away. Continue to offer treats, but sometimes move your hand over without the treat. Don't try to touch them yet and don't chase after them if they move away. Your goal is to let them get used to your hand moving close to them without doing anything scary.
In time, they should let you get closer. Don't push too hard or too fast. Let the bird set the pace. Encourage them to approach YOU and talk gently when the bird is brave so he knows you are not a threat. Parakeets are awesome little birds. You will be good friends some day, I know it.
Good luck!
