Multi page form with one ID (identifier) common to all forms

Multi page form with one ID (identifier) common to all forms

I have an application with multiple Forms - Form A, Form B, Form C and Form D. I want one ID or identifier to be common to all four forms, say username. But I dont want users to type username everytime in every form.

Lookup Field creates a dropdown menu...which I dont want. Is there a way Form B automatically Loads the username from Form A?