Once twins find out they live powerful family and part of a prophecy, are rescued from Earth, they must fulfill their destiny to destroy the dictator.
Yup, for starters, the language needs to be clear.
Add specifics and missing parts. Are the twins two girls or two boys or one of each? Are they teens? Dictator where? What’s the difficulty in destroying him or what’s the plan? What are the stakes, what would happen if they fail?
Is a prophecy really needed? They’re so overdone, which means it needs an especially fresh angle or twist to tell readers that this writer is being original.