Alzheimer's Disease - forgetting more than normal.

I am a 15 year old boy. My grandfather is recently starting to forget more than normal. He just turned 77. He lives with us. I always know that older people forget some things but in the recent days I have reason to believe that he is forgetting more than normal. Once reason is that we had some guests come over and my grandmother had confirmed with my grandfather if he wants to invite them. Later on, in the same day he asked again who are we going to invite. He forgot. Another thing is today my brother went to Taekwondo. My grandfather asked what sport classes did you go to. My brother replied he went to Taekwondo. 5-10 minutes later he asked whether my brother had Taekwondo. Also since my uncle is coming in a few days, my grandfather asked how is he going to come. My mom replied by rental car. 2 minutes later he asked a different question but wanted the same info. My question is as a 15 year old with limited resources, what can I do to highlight my grandfather's symptoms to my parents without them getting panicked or letting them think as if there is nothing to it. These incidents were incidents where he asked for the same info in relatively short amount of time.