Your brother is likely having Seizures or Scar Epilepsy
from the previous stroke
he suffered. The weakness of the Right side you mention is either due to Todds Palsy
or a residual effect of the Previous strokes getting accentuated.(you havent mentioned which side he had stroke earlier.)
Consult your doctor and add antiepileptic medications if he is not on them already or to adjust the dose if he is on them already.Hope this helps.