"Homer Simpson is Marge Simpson's husband."
Is this a true statement since it accurately describes the fictional character, Homer Simpson, or is it false since there is no Homer Simpson in reality to begin with?
They are really neither true or false, they are modal. In particular they are in the modality 'would (given X)' along with scientific hypotheticals and counterfactual statements.
(Meanwhile, if you absolutely had to assign them a truth value, Quine suggests it would be vacuously true, as long as the statements do not explicitly assert existence. All unicorns are black when there are no unicorns. Any given description applies to all zero of the intended Homer Simpsons found in the real world. There is bound to be some context that would make them true unless they absolutely require objects to exist.)
There is an interpretation of all modals that makes them wrong to interpret without an attached context. The fictional world is just an example of such an attached context. Modal statements are true or false given that the fictional world is the world of reference, and vacuously true but not helpful otherwise.
I gave this same answer with more context here and don't want to repeat it.