JH,
My parents were 40 & 45 when I was born, so by the time I got into my 30's they were 70 & 75, my being the youngest it fell to me to take care of them in their old age.
I used to get irritated with my folks too, they could not seem to understand even the most simple thing like you mentioned. I took care of them in my home till they passed for 5 years. Dad died first at 85 then Mom lived 5 more years and she died at 85 too. Mom would get all mixed up in her 70's and later I found out that both of my parents suffered from harding of the arteries. Which meant less blood flow from heart to the brain and affected their ability to think clearly. It explained why my mother was so forgetful, especially her short term memory did't exist. By the time they were in their 80's I was 40 myself.
I hear myself doing and saying the same darn stupid things to my sons that irritated me about my Mom. The point is you're aging yourself and will have some of the same irritating behavior that drove you crazy about your own parents. The thing is I'm an older parent myself, my boys came along when I was in my 30's. My youngest son constantly reminds me Mom you just asked me that. Mom why do you keep saying that. I can see right now he will have little to do with me in my old age because he is so irritated by my getting old and acting it.
As we age our minds don't work as clearly as we would like them too. We slow down to the point that we barely feel like we're moving. Be patient with them, don't become angry. Realize that most of it is just the natural process of aging. I learned a lot taking care of my parents, after a while I quit correcting them, it stressed me out and hurt them and was down right cruel. Think what will it hurt if they say it wrong? As for your Dad and him not hearing you, it could be that his brain is trying to catch on to what your saying and once it does he is hearing you. But at the beginning you have to do a lot of repeating.
As the old saying goes " Do unto others as you would have them do unto you" Imagine yourself their age, find out what it is like and have a little understand. My brother who was 13 years older than me had no patience with my folks when he visited them, and it was really hurtful to them. There are some wonderful books on dealing with aging parents, I recommend you read some of them.
I'm 55 now and disabled I understand so much more now than I did when I was younger, and you will too. Learn patience before you blow a gasket at one or the other of them. Oh and never talk to them across the room, make sure they can see you, and yell if you need to so they can hear you. I've still got my Mom's hearing aid, I get them out and look at them sometmes and think it won't be long before I need them myself. Look at your Dad and realize one day that is going to be you.
Balsam