my brother, although only 30, had similar symptoms.
he was getting severe headaches, migraines, and 'pressure' behind left eye. as like you, as a family, we all thought the worst. he had a ct scan which showed a grey area on the brain, and then a MRI. it turned out to be a polyp in his sinus. he had this removed, and 6 weeks on is fit as ever. biopsy results all clear!!
i know this might have no bearing on what your relative has, but thought it mite reassure you that not all symptoms lead to cancer. i know it's easier said than done, but just stay positive, and keep motivated.
I'd like to also add that my brother was battling bacterial meningitis at same time as they found polyp, so if he can do all that, then I'm sure many others will