Could you tell me what happens to the pupils when you have a stroke or brain aneurysm?

Depends: Pupil constriction is controlled by the oculomotor nerve. If a stroke involves the brainstem (nucleus of the nerve) or an aneurysm pushes on the nerve itself then the pupil involved may look different from the normal opposite side. Many strokes will have no effect at all on pupil size.

Variable: Depends on part of brain nerves to eyes threatened. Aneurysm may have unilateral signs dilation brain death dilated fixed wide pupils. Depends.