Final answer:
The pronoun 'thou' in this line from Shakespeare's Hamlet refers to the character of Hamlet himself.
Step-by-step explanation:
The line 'If thou didst ever hold me in thy heart.../And in this harsh world draw thy breath in pain/To tell my story' is from Hamlet by William Shakespeare. The pronoun 'thou' in this line refers to the character of Hamlet himself. In this soliloquy, Hamlet is contemplating his own mortality and questioning if anyone will remember his story after he is gone. Shakespeare often used the pronoun 'thou' as a way of addressing and referring to a single person in a poetic and dramatic manner.