A stroke wil affect people in different ways depending on which part of the brain was involved. Frontal lobe strokes cause changes in personality, but even these vary a lot.
This can be more difficult for the family to cope with than a stoke which causes weakness or paralysis, because you are your personality. It is easy to see physical weakness, but difficult to see why a person has changed.
I know a complete gentleman who had a stroke and know swears a lot and is very sexually explicit.
Hang in there. Try and tell your grandfather what is appropriate and what is not, remembering that his memory and ability to understand will mean he will probably forget. With some people signs are helpful. ie one near the door saying do not not go somewhere etc if it is becoming an issue.
The human brain is extremely complex, more so than could ever be explained here. Strokes have many different causes and even more outcomes. First of all let me say that your grandfather is VERY lucky to have came out of it as well as it sounds like he did. Minor peronality changes are not abnormal. As the person above said, different parts of the brain conrtol and effect different things. Frontol lobe is personality, human interaction, social behavior etc. While the cerebellum, for example, controls motor function, balance, speech, and some cognitive function. It all has to do with the part of the brain that was injured or effected by the stroke, as well as what type of stroke it was. For exaple, an infarct or blockage can cause permanent brain death of a portion of the brain. And symptoms of a hemmorhage or bleeding stroke can slowly resolve over time. Most likely what it sounds like is going on with your grandfather, is that there really isnt too much actual brain damage, probably more psychological damage. Meaning, he had a scare, and as we age we realize more and more about our own mortality. He wants to make sure he is visiting his friends before they or he is gone. He also has something in common with his friend, so he can relate to him, as they have both been through a very scary ordeal. He is very lucky. The stroke patients I see everyday cannot walk, wipe themselves, or even swallow (can you imagine not being able to drink water without gelatin mixed in it so you dont choke on it?). My recommendation is you should use this oppourtunity to learn more about the human brain. Take classes, find out what and why. My mom has epilepsy, and after growing up watching her have terrifying seizures, I wanted to find out why and what I could do, so I did. So you could do the same. Good Luck to you, and your grandpa. Spend time with him, tell him you love him, make sure he knows.